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Andreas Peters 2 years ago

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.gitignore View File

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.travis.yml View File

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# Continuous Integration (CI) is the practice, in software
# engineering, of merging all developer working copies with a shared mainline
# several times a day < >
# Documentation:
# * Travis CI Embedded Builds with PlatformIO
# < >
# * PlatformIO integration with Travis CI
# < >
# * User Guide for `platformio ci` command
# < >
# Please choice one of the following templates (proposed below) and uncomment
# it (remove "# " before each line) or use own configuration according to the
# Travis CI documentation (see above).

# Template #1: General project. Test it using existing `platformio.ini`.

# language: python
# python:
# - "2.7"
# sudo: false
# cache:
# directories:
# - "~/.platformio"
# install:
# - pip install -U platformio
# script:
# - platformio run

# Template #2: The project is intended to by used as a library with examples

# language: python
# python:
# - "2.7"
# sudo: false
# cache:
# directories:
# - "~/.platformio"
# env:
# - PLATFORMIO_CI_SRC=path/to/test/file.c
# - PLATFORMIO_CI_SRC=examples/file.ino
# - PLATFORMIO_CI_SRC=path/to/test/directory
# install:
# - pip install -U platformio
# script:
# - platformio ci --lib="." --board=ID_1 --board=ID_2 --board=ID_N

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lib/LibAPRS/AFSK.cpp View File

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#include <string.h>
#include "AFSK.h"
#include "Arduino.h"

extern unsigned long custom_preamble;
extern unsigned long custom_tail;
extern int LibAPRS_vref;
extern bool LibAPRS_open_squelch;

bool hw_afsk_dac_isr = false;
bool hw_5v_ref = false;
Afsk *AFSK_modem;

// Forward declerations
int afsk_getchar(void);
void afsk_putchar(char c);

void AFSK_hw_refDetect(void) {
// This is manual for now
if (LibAPRS_vref == REF_5V) {
hw_5v_ref = true;
} else {
hw_5v_ref = false;

void AFSK_hw_init(void) {
// Set up ADC


TCCR1A = 0;
TCCR1B = _BV(CS10) | _BV(WGM13) | _BV(WGM12);

if (hw_5v_ref) {
ADMUX = _BV(REFS0) | 0;
} else {
ADMUX = 0;

ADC_DDR &= ~_BV(0);
ADC_PORT &= ~_BV(0);
DIDR0 |= _BV(0);
_BV(ADTS1) |


void AFSK_init(Afsk *afsk) {
// Allocate modem struct memory
memset(afsk, 0, sizeof(*afsk));
AFSK_modem = afsk;
// Set phase increment
afsk->phaseInc = MARK_INC;
// Initialise FIFO buffers
fifo_init(&afsk->delayFifo, (uint8_t *)afsk->delayBuf, sizeof(afsk->delayBuf));
fifo_init(&afsk->rxFifo, afsk->rxBuf, sizeof(afsk->rxBuf));
fifo_init(&afsk->txFifo, afsk->txBuf, sizeof(afsk->txBuf));

// Fill delay FIFO with zeroes
for (int i = 0; i<SAMPLESPERBIT / 2; i++) {
fifo_push(&afsk->delayFifo, 0);



static void AFSK_txStart(Afsk *afsk) {
if (!afsk->sending) {
afsk->phaseInc = MARK_INC;
afsk->phaseAcc = 0;
afsk->bitstuffCount = 0;
afsk->sending = true;
afsk->preambleLength = DIV_ROUND(custom_preamble * BITRATE, 8000);
afsk->tailLength = DIV_ROUND(custom_tail * BITRATE, 8000);

void afsk_putchar(char c) {
while(fifo_isfull_locked(&AFSK_modem->txFifo)) { /* Wait */ }
fifo_push_locked(&AFSK_modem->txFifo, c);

int afsk_getchar(void) {
if (fifo_isempty_locked(&AFSK_modem->rxFifo)) {
return EOF;
} else {
return fifo_pop_locked(&AFSK_modem->rxFifo);

void AFSK_transmit(char *buffer, size_t size) {
int i = 0;
while (size--) {

uint8_t AFSK_dac_isr(Afsk *afsk) {
if (afsk->sampleIndex == 0) {
if (afsk->txBit == 0) {
if (fifo_isempty(&afsk->txFifo) && afsk->tailLength == 0) {
afsk->sending = false;
return 0;
} else {
if (!afsk->bitStuff) afsk->bitstuffCount = 0;
afsk->bitStuff = true;
if (afsk->preambleLength == 0) {
if (fifo_isempty(&afsk->txFifo)) {
afsk->currentOutputByte = HDLC_FLAG;
} else {
afsk->currentOutputByte = fifo_pop(&afsk->txFifo);
} else {
afsk->currentOutputByte = HDLC_FLAG;
if (afsk->currentOutputByte == AX25_ESC) {
if (fifo_isempty(&afsk->txFifo)) {
afsk->sending = false;
return 0;
} else {
afsk->currentOutputByte = fifo_pop(&afsk->txFifo);
} else if (afsk->currentOutputByte == HDLC_FLAG || afsk->currentOutputByte == HDLC_RESET) {
afsk->bitStuff = false;
afsk->txBit = 0x01;

if (afsk->bitStuff && afsk->bitstuffCount >= BIT_STUFF_LEN) {
afsk->bitstuffCount = 0;
afsk->phaseInc = SWITCH_TONE(afsk->phaseInc);
} else {
if (afsk->currentOutputByte & afsk->txBit) {
} else {
afsk->bitstuffCount = 0;
afsk->phaseInc = SWITCH_TONE(afsk->phaseInc);
afsk->txBit <<= 1;

afsk->sampleIndex = SAMPLESPERBIT;

afsk->phaseAcc += afsk->phaseInc;
afsk->phaseAcc %= SIN_LEN;

return sinSample(afsk->phaseAcc);

static bool hdlcParse(Hdlc *hdlc, bool bit, FIFOBuffer *fifo) {
// Initialise a return value. We start with the
// assumption that all is going to end well :)
bool ret = true;

// Bitshift our byte of demodulated bits to
// the left by one bit, to make room for the
// next incoming bit
hdlc->demodulatedBits <<= 1;
// And then put the newest bit from the
// demodulator into the byte.
hdlc->demodulatedBits |= bit ? 1 : 0;

// Now we'll look at the last 8 received bits, and
// check if we have received a HDLC flag (01111110)
if (hdlc->demodulatedBits == HDLC_FLAG) {
// If we have, check that our output buffer is
// not full.
if (!fifo_isfull(fifo)) {
// If it isn't, we'll push the HDLC_FLAG into
// the buffer and indicate that we are now
// receiving data. For bling we also turn
// on the RX LED.
fifo_push(fifo, HDLC_FLAG);
hdlc->receiving = true;
if(!LibAPRS_open_squelch) {
} else {
// If the buffer is full, we have a problem
// and abort by setting the return value to
// false and stopping the here.
ret = false;
hdlc->receiving = false;

// Everytime we receive a HDLC_FLAG, we reset the
// storage for our current incoming byte and bit
// position in that byte. This effectively
// synchronises our parsing to the start and end
// of the received bytes.
hdlc->currentByte = 0;
hdlc->bitIndex = 0;
return ret;

// Check if we have received a RESET flag (01111111)
// In this comparison we also detect when no transmission
// (or silence) is taking place, and the demodulator
// returns an endless stream of zeroes. Due to the NRZ
// coding, the actual bits send to this function will
// be an endless stream of ones, which this AND operation
// will also detect.
if ((hdlc->demodulatedBits & HDLC_RESET) == HDLC_RESET) {
// If we have, something probably went wrong at the
// transmitting end, and we abort the reception.
hdlc->receiving = false;
return ret;

// If we have not yet seen a HDLC_FLAG indicating that
// a transmission is actually taking place, don't bother
// with anything.
if (!hdlc->receiving)
return ret;

// First check if what we are seeing is a stuffed bit.
// Since the different HDLC control characters like
// HDLC_FLAG, HDLC_RESET and such could also occur in
// a normal data stream, we employ a method known as
// "bit stuffing". All control characters have more than
// 5 ones in a row, so if the transmitting party detects
// this sequence in the _data_ to be transmitted, it inserts
// a zero to avoid the receiving party interpreting it as
// a control character. Therefore, if we detect such a
// "stuffed bit", we simply ignore it and wait for the
// next bit to come in.
// We do the detection by applying an AND bit-mask to the
// stream of demodulated bits. This mask is 00111111 (0x3f)
// if the result of the operation is 00111110 (0x3e), we
// have detected a stuffed bit.
if ((hdlc->demodulatedBits & 0x3f) == 0x3e)
return ret;

// If we have an actual 1 bit, push this to the current byte
// If it's a zero, we don't need to do anything, since the
// bit is initialized to zero when we bitshifted earlier.
if (hdlc->demodulatedBits & 0x01)
hdlc->currentByte |= 0x80;

// Increment the bitIndex and check if we have a complete byte
if (++hdlc->bitIndex >= 8) {
// If we have a HDLC control character, put a AX.25 escape
// in the received data. We know we need to do this,
// because at this point we must have already seen a HDLC
// flag, meaning that this control character is the result
// of a bitstuffed byte that is equal to said control
// character, but is actually part of the data stream.
// By inserting the escape character, we tell the protocol
// layer that this is not an actual control character, but
// data.
if ((hdlc->currentByte == HDLC_FLAG ||
hdlc->currentByte == HDLC_RESET ||
hdlc->currentByte == AX25_ESC)) {
// We also need to check that our received data buffer
// is not full before putting more data in
if (!fifo_isfull(fifo)) {
fifo_push(fifo, AX25_ESC);
} else {
// If it is, abort and return false
hdlc->receiving = false;
ret = false;

// Push the actual byte to the received data FIFO,
// if it isn't full.
if (!fifo_isfull(fifo)) {
fifo_push(fifo, hdlc->currentByte);
} else {
// If it is, well, you know by now!
hdlc->receiving = false;
ret = false;

// Wipe received byte and reset bit index to 0
hdlc->currentByte = 0;
hdlc->bitIndex = 0;

} else {
// We don't have a full byte yet, bitshift the byte
// to make room for the next bit
hdlc->currentByte >>= 1;

//digitalWrite(13, LOW);
return ret;

void AFSK_adc_isr(Afsk *afsk, int8_t currentSample) {
// To determine the received frequency, and thereby
// the bit of the sample, we multiply the sample by
// a sample delayed by (samples per bit / 2).
// We then lowpass-filter the samples with a
// Chebyshev filter. The lowpass filtering serves
// to "smooth out" the variations in the samples.

afsk->iirX[0] = afsk->iirX[1];
afsk->iirX[1] = ((int8_t)fifo_pop(&afsk->delayFifo) * currentSample) >> 2;

afsk->iirY[0] = afsk->iirY[1];
afsk->iirY[1] = afsk->iirX[0] + afsk->iirX[1] + (afsk->iirY[0] >> 1); // Chebyshev filter

// We put the sampled bit in a delay-line:
// First we bitshift everything 1 left
afsk->sampledBits <<= 1;
// And then add the sampled bit to our delay line
afsk->sampledBits |= (afsk->iirY[1] > 0) ? 1 : 0;

// Put the current raw sample in the delay FIFO
fifo_push(&afsk->delayFifo, currentSample);

// We need to check whether there is a signal transition.
// If there is, we can recalibrate the phase of our
// sampler to stay in sync with the transmitter. A bit of
// explanation is required to understand how this works.
// Since we have PHASE_MAX/PHASE_BITS = 8 samples per bit,
// we employ a phase counter (currentPhase), that increments
// by PHASE_BITS everytime a sample is captured. When this
// counter reaches PHASE_MAX, it wraps around by modulus
// PHASE_MAX. We then look at the last three samples we
// captured and determine if the bit was a one or a zero.
// This gives us a "window" looking into the stream of
// samples coming from the ADC. Sort of like this:
// Past Future
// 0000000011111111000000001111111100000000
// |________|
// ||
// Window
// Every time we detect a signal transition, we adjust
// where this window is positioned little. How much we
// adjust it is defined by PHASE_INC. If our current phase
// phase counter value is less than half of PHASE_MAX (ie,
// the window size) when a signal transition is detected,
// add PHASE_INC to our phase counter, effectively moving
// the window a little bit backward (to the left in the
// illustration), inversely, if the phase counter is greater
// than half of PHASE_MAX, we move it forward a little.
// This way, our "window" is constantly seeking to position
// it's center at the bit transitions. Thus, we synchronise
// our timing to the transmitter, even if it's timing is
// a little off compared to our own.
if (SIGNAL_TRANSITIONED(afsk->sampledBits)) {
if (afsk->currentPhase < PHASE_THRESHOLD) {
afsk->currentPhase += PHASE_INC;
} else {
afsk->currentPhase -= PHASE_INC;

// We increment our phase counter
afsk->currentPhase += PHASE_BITS;

// Check if we have reached the end of
// our sampling window.
if (afsk->currentPhase >= PHASE_MAX) {
// If we have, wrap around our phase
// counter by modulus
afsk->currentPhase %= PHASE_MAX;

// Bitshift to make room for the next
// bit in our stream of demodulated bits
afsk->actualBits <<= 1;

// We determine the actual bit value by reading
// the last 3 sampled bits. If there is three or
// more 1's, we will assume that the transmitter
// sent us a one, otherwise we assume a zero
uint8_t bits = afsk->sampledBits & 0x07;
if (bits == 0x07 || // 111
bits == 0x06 || // 110
bits == 0x05 || // 101
bits == 0x03 // 011
) {
afsk->actualBits |= 1;

//// Alternative using five bits ////////////////
// uint8_t bits = afsk->sampledBits & 0x0f;
// uint8_t c = 0;
// c += bits & BV(1);
// c += bits & BV(2);
// c += bits & BV(3);
// c += bits & BV(4);
// c += bits & BV(5);
// if (c >= 3) afsk->actualBits |= 1;

// Now we can pass the actual bit to the HDLC parser.
// We are using NRZ coding, so if 2 consecutive bits
// have the same value, we have a 1, otherwise a 0.
// We use the TRANSITION_FOUND function to determine this.
// This is smart in combination with bit stuffing,
// since it ensures a transmitter will never send more
// than five consecutive 1's. When sending consecutive
// ones, the signal stays at the same level, and if
// this happens for longer periods of time, we would
// not be able to synchronize our phase to the transmitter
// and would start experiencing "bit slip".
// By combining bit-stuffing with NRZ coding, we ensure
// that the signal will regularly make transitions
// that we can use to synchronize our phase.
// We also check the return of the Link Control parser
// to check if an error occured.

if (!hdlcParse(&afsk->hdlc, !TRANSITION_FOUND(afsk->actualBits), &afsk->rxFifo)) {
afsk->status |= 1;
if (fifo_isfull(&afsk->rxFifo)) {
afsk->status = 0;


extern void APRS_poll();
uint8_t poll_timer = 0;
ISR(ADC_vect) {
TIFR1 = _BV(ICF1);
AFSK_adc_isr(AFSK_modem, ((int16_t)((ADC) >> 2) - 128));
if (hw_afsk_dac_isr) {
DAC_PORT = (AFSK_dac_isr(AFSK_modem) & 0xF0) | _BV(3);
} else {
DAC_PORT = 128;

if (poll_timer > 3) {
poll_timer = 0;

+ 138
- 0
lib/LibAPRS/AFSK.h View File

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#ifndef AFSK_H
#define AFSK_H

#include "device.h"
#include <stdint.h>
#include <stdbool.h>
#include <stdio.h>
#include <avr/pgmspace.h>
#include "FIFO.h"
#include "HDLC.h"

#define SIN_LEN 512
static const uint8_t sin_table[] PROGMEM =
128, 129, 131, 132, 134, 135, 137, 138, 140, 142, 143, 145, 146, 148, 149, 151,
152, 154, 155, 157, 158, 160, 162, 163, 165, 166, 167, 169, 170, 172, 173, 175,
176, 178, 179, 181, 182, 183, 185, 186, 188, 189, 190, 192, 193, 194, 196, 197,
198, 200, 201, 202, 203, 205, 206, 207, 208, 210, 211, 212, 213, 214, 215, 217,
218, 219, 220, 221, 222, 223, 224, 225, 226, 227, 228, 229, 230, 231, 232, 233,
234, 234, 235, 236, 237, 238, 238, 239, 240, 241, 241, 242, 243, 243, 244, 245,
245, 246, 246, 247, 248, 248, 249, 249, 250, 250, 250, 251, 251, 252, 252, 252,
253, 253, 253, 253, 254, 254, 254, 254, 254, 255, 255, 255, 255, 255, 255, 255,

inline static uint8_t sinSample(uint16_t i) {
uint16_t newI = i % (SIN_LEN/2);
newI = (newI >= (SIN_LEN/4)) ? (SIN_LEN/2 - newI -1) : newI;
uint8_t sine = pgm_read_byte(&sin_table[newI]);
return (i >= (SIN_LEN/2)) ? (255 - sine) : sine;

#define SWITCH_TONE(inc) (((inc) == MARK_INC) ? SPACE_INC : MARK_INC)
#define BITS_DIFFER(bits1, bits2) (((bits1)^(bits2)) & 0x01)
#define DUAL_XOR(bits1, bits2) ((((bits1)^(bits2)) & 0x03) == 0x03)
#define SIGNAL_TRANSITIONED(bits) DUAL_XOR((bits), (bits) >> 2)
#define TRANSITION_FOUND(bits) BITS_DIFFER((bits), (bits) >> 1)

#define CPU_FREQ F_CPU

#define SAMPLERATE 9600
#define BITRATE 1200
#define BIT_STUFF_LEN 5
#define MARK_FREQ 1200
#define SPACE_FREQ 2200
#define PHASE_BITS 8 // How much to increment phase counter each sample
#define PHASE_INC 1 // Nudge by an eigth of a sample each adjustment
#define PHASE_MAX (SAMPLESPERBIT * PHASE_BITS) // Resolution of our phase counter = 64
#define PHASE_THRESHOLD (PHASE_MAX / 2) // Target transition point of our phase window

typedef struct Hdlc
uint8_t demodulatedBits;
uint8_t bitIndex;
uint8_t currentByte;
bool receiving;
} Hdlc;

typedef struct Afsk
// Stream access to modem
FILE fd;

// General values
Hdlc hdlc; // We need a link control structure
uint16_t preambleLength; // Length of sync preamble
uint16_t tailLength; // Length of transmission tail

// Modulation values
uint8_t sampleIndex; // Current sample index for outgoing bit
uint8_t currentOutputByte; // Current byte to be modulated
uint8_t txBit; // Mask of current modulated bit
bool bitStuff; // Whether bitstuffing is allowed

uint8_t bitstuffCount; // Counter for bit-stuffing

uint16_t phaseAcc; // Phase accumulator
uint16_t phaseInc; // Phase increment per sample

FIFOBuffer txFifo; // FIFO for transmit data
uint8_t txBuf[CONFIG_AFSK_TX_BUFLEN]; // Actial data storage for said FIFO

volatile bool sending; // Set when modem is sending

// Demodulation values
FIFOBuffer delayFifo; // Delayed FIFO for frequency discrimination
int8_t delayBuf[SAMPLESPERBIT / 2 + 1]; // Actual data storage for said FIFO

FIFOBuffer rxFifo; // FIFO for received data
uint8_t rxBuf[CONFIG_AFSK_RX_BUFLEN]; // Actual data storage for said FIFO

int16_t iirX[2]; // IIR Filter X cells
int16_t iirY[2]; // IIR Filter Y cells

uint8_t sampledBits; // Bits sampled by the demodulator (at ADC speed)
int8_t currentPhase; // Current phase of the demodulator
uint8_t actualBits; // Actual found bits at correct bitrate

volatile int status; // Status of the modem, 0 means OK

} Afsk;

#define DIV_ROUND(dividend, divisor) (((dividend) + (divisor) / 2) / (divisor))

#define AFSK_DAC_IRQ_START() do { extern bool hw_afsk_dac_isr; hw_afsk_dac_isr = true; } while (0)
#define AFSK_DAC_IRQ_STOP() do { extern bool hw_afsk_dac_isr; hw_afsk_dac_isr = false; } while (0)
#define AFSK_DAC_INIT() do { DAC_DDR |= 0xF8; } while (0)

// Here's some macros for controlling the RX/TX LEDs
// THE _INIT() functions writes to the DDRB register
// to configure the pins as output pins, and the _ON()
// and _OFF() functions writes to the PORT registers
// to turn the pins on or off.
#define LED_TX_INIT() do { LED_DDR |= _BV(1); } while (0)
#define LED_TX_ON() do { LED_PORT |= _BV(1); } while (0)
#define LED_TX_OFF() do { LED_PORT &= ~_BV(1); } while (0)

#define LED_RX_INIT() do { LED_DDR |= _BV(2); } while (0)
#define LED_RX_ON() do { LED_PORT |= _BV(2); } while (0)
#define LED_RX_OFF() do { LED_PORT &= ~_BV(2); } while (0)

void AFSK_init(Afsk *afsk);
void AFSK_transmit(char *buffer, size_t size);
void AFSK_poll(Afsk *afsk);

void afsk_putchar(char c);
int afsk_getchar(void);


+ 164
- 0
lib/LibAPRS/AX25.cpp View File

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// Based on work by Francesco Sacchi

#include "Arduino.h"
#include <string.h>
#include <ctype.h>
#include "AX25.h"
#include "HDLC.h"
#include "CRC-CCIT.h"
#include "AFSK.h"

#define countof(a) sizeof(a)/sizeof(a[0])
#define MIN(a,b) ({ typeof(a) _a = (a); typeof(b) _b = (b); ((typeof(_a))((_a < _b) ? _a : _b)); })
#define DECODE_CALL(buf, addr) for (unsigned i = 0; i < sizeof((addr))-CALL_OVERSPACE; i++) { char c = (*(buf)++ >> 1); (addr)[i] = (c == ' ') ? '\x0' : c; }
#define AX25_SET_REPEATED(msg, idx, val) do { if (val) { (msg)->rpt_flags |= _BV(idx); } else { (msg)->rpt_flags &= ~_BV(idx) ; } } while(0)

extern int LibAPRS_vref;
extern bool LibAPRS_open_squelch;

void ax25_init(AX25Ctx *ctx, ax25_callback_t hook) {
memset(ctx, 0, sizeof(*ctx));
ctx->hook = hook;
ctx->crc_in = ctx->crc_out = CRC_CCIT_INIT_VAL;

static void ax25_decode(AX25Ctx *ctx) {
AX25Msg msg;
uint8_t *buf = ctx->buf;

msg.dst.ssid = (*buf++ >> 1) & 0x0F;[6] = 0;

msg.src.ssid = (*buf >> 1) & 0x0F;[6] = 0;

for (msg.rpt_count = 0; !(*buf++ & 0x01) && (msg.rpt_count < countof(msg.rpt_list)); msg.rpt_count++) {
DECODE_CALL(buf, msg.rpt_list[msg.rpt_count].call);
msg.rpt_list[msg.rpt_count].ssid = (*buf >> 1) & 0x0F;
AX25_SET_REPEATED(&msg, msg.rpt_count, (*buf & 0x80));

msg.ctrl = *buf++;
if (msg.ctrl != AX25_CTRL_UI) { return; } = *buf++;
if ( != AX25_PID_NOLAYER3) { return; }

msg.len = ctx->frame_len - 2 - (buf - ctx->buf); = buf;

if (ctx->hook) {


void ax25_poll(AX25Ctx *ctx) {
int c;

while ((c = afsk_getchar()) != EOF) {
if (!ctx->escape && c == HDLC_FLAG) {
if (ctx->frame_len >= AX25_MIN_FRAME_LEN) {
if (ctx->crc_in == AX25_CRC_CORRECT) {
if(LibAPRS_open_squelch) {
ctx->sync = true;
ctx->crc_in = CRC_CCIT_INIT_VAL;
ctx->frame_len = 0;

if (!ctx->escape && c == HDLC_RESET) {
ctx->sync = false;

if (!ctx->escape && c == AX25_ESC) {
ctx->escape = true;

if (ctx->sync) {
if (ctx->frame_len < AX25_MAX_FRAME_LEN) {
ctx->buf[ctx->frame_len++] = c;
ctx->crc_in = update_crc_ccit(c, ctx->crc_in);
} else {
ctx->sync = false;
ctx->escape = false;

static void ax25_putchar(AX25Ctx *ctx, uint8_t c)
if (c == HDLC_FLAG || c == HDLC_RESET || c == AX25_ESC) afsk_putchar(AX25_ESC);
ctx->crc_out = update_crc_ccit(c, ctx->crc_out);

void ax25_sendRaw(AX25Ctx *ctx, void *_buf, size_t len) {
ctx->crc_out = CRC_CCIT_INIT_VAL;
const uint8_t *buf = (const uint8_t *)_buf;
while (len--) ax25_putchar(ctx, *buf++);

uint8_t crcl = (ctx->crc_out & 0xff) ^ 0xff;
uint8_t crch = (ctx->crc_out >> 8) ^ 0xff;
ax25_putchar(ctx, crcl);
ax25_putchar(ctx, crch);


static void ax25_sendCall(AX25Ctx *ctx, const AX25Call *addr, bool last){
unsigned len = MIN((sizeof(addr->call) - CALL_OVERSPACE), strlen(addr->call));

for (unsigned i = 0; i < len; i++) {
uint8_t c = addr->call[i];
c = toupper(c);
ax25_putchar(ctx, c << 1);

if (len < (sizeof(addr->call) - CALL_OVERSPACE)) {
for (unsigned i = 0; i < (sizeof(addr->call) - CALL_OVERSPACE) - len; i++) {
ax25_putchar(ctx, ' ' << 1);

uint8_t ssid = 0x60 | (addr->ssid << 1) | (last ? 0x01 : 0);
ax25_putchar(ctx, ssid);

void ax25_sendVia(AX25Ctx *ctx, const AX25Call *path, size_t path_len, const void *_buf, size_t len) {
const uint8_t *buf = (const uint8_t *)_buf;

ctx->crc_out = CRC_CCIT_INIT_VAL;

for (size_t i = 0; i < path_len; i++) {
ax25_sendCall(ctx, &path[i], (i == path_len - 1));

ax25_putchar(ctx, AX25_CTRL_UI);
ax25_putchar(ctx, AX25_PID_NOLAYER3);

while (len--) {
ax25_putchar(ctx, *buf++);

uint8_t crcl = (ctx->crc_out & 0xff) ^ 0xff;
uint8_t crch = (ctx->crc_out >> 8) ^ 0xff;
ax25_putchar(ctx, crcl);
ax25_putchar(ctx, crch);


+ 70
- 0
lib/LibAPRS/AX25.h View File

@@ -0,0 +1,70 @@
#ifndef PROTOCOL_AX25_H
#define PROTOCOL_AX25_H

#include <stdio.h>
#include <stdbool.h>
#include "device.h"

#define AX25_MIN_FRAME_LEN 18
#define AX25_MAX_FRAME_LEN 330

#define AX25_CRC_CORRECT 0xF0B8

#define AX25_CTRL_UI 0x03
#define AX25_PID_NOLAYER3 0xF0

struct AX25Ctx; // Forward declarations
struct AX25Msg;

typedef void (*ax25_callback_t)(struct AX25Msg *msg);

typedef struct AX25Ctx {
uint8_t buf[AX25_MAX_FRAME_LEN];
FILE *ch;
size_t frame_len;
uint16_t crc_in;
uint16_t crc_out;
ax25_callback_t hook;
bool sync;
bool escape;
} AX25Ctx;

#define AX25_CALL(str, id) {.call = (str), .ssid = (id) }
#define AX25_MAX_RPT 8
#define AX25_REPEATED(msg, n) ((msg)->rpt_flags & BV(n))


typedef struct AX25Call {
char call[6+CALL_OVERSPACE];
uint8_t ssid;
} AX25Call;

typedef struct AX25Msg {
AX25Call src;
AX25Call dst;
AX25Call rpt_list[AX25_MAX_RPT];
uint8_t rpt_count;
uint8_t rpt_flags;
uint16_t ctrl;
uint8_t pid;
const uint8_t *info;
size_t len;
} AX25Msg;

void ax25_sendVia(AX25Ctx *ctx, const AX25Call *path, size_t path_len, const void *_buf, size_t len);
#define ax25_send(ctx, dst, src, buf, len) ax25_sendVia(ctx, ({static AX25Call __path[]={dst, src}; __path;}), 2, buf, len)

void ax25_poll(AX25Ctx *ctx);
void ax25_sendRaw(AX25Ctx *ctx, void *_buf, size_t len);
void ax25_init(AX25Ctx *ctx, ax25_callback_t hook);


+ 36
- 0
lib/LibAPRS/CRC-CCIT.c View File

@@ -0,0 +1,36 @@
#include "CRC-CCIT.h"

const uint16_t crc_ccit_table[256] PROGMEM = {
0x0000, 0x1189, 0x2312, 0x329b, 0x4624, 0x57ad, 0x6536, 0x74bf,
0x8c48, 0x9dc1, 0xaf5a, 0xbed3, 0xca6c, 0xdbe5, 0xe97e, 0xf8f7,
0x1081, 0x0108, 0x3393, 0x221a, 0x56a5, 0x472c, 0x75b7, 0x643e,
0x9cc9, 0x8d40, 0xbfdb, 0xae52, 0xdaed, 0xcb64, 0xf9ff, 0xe876,
0x2102, 0x308b, 0x0210, 0x1399, 0x6726, 0x76af, 0x4434, 0x55bd,
0xad4a, 0xbcc3, 0x8e58, 0x9fd1, 0xeb6e, 0xfae7, 0xc87c, 0xd9f5,
0x3183, 0x200a, 0x1291, 0x0318, 0x77a7, 0x662e, 0x54b5, 0x453c,
0xbdcb, 0xac42, 0x9ed9, 0x8f50, 0xfbef, 0xea66, 0xd8fd, 0xc974,
0x4204, 0x538d, 0x6116, 0x709f, 0x0420, 0x15a9, 0x2732, 0x36bb,
0xce4c, 0xdfc5, 0xed5e, 0xfcd7, 0x8868, 0x99e1, 0xab7a, 0xbaf3,
0x5285, 0x430c, 0x7197, 0x601e, 0x14a1, 0x0528, 0x37b3, 0x263a,
0xdecd, 0xcf44, 0xfddf, 0xec56, 0x98e9, 0x8960, 0xbbfb, 0xaa72,
0x6306, 0x728f, 0x4014, 0x519d, 0x2522, 0x34ab, 0x0630, 0x17b9,
0xef4e, 0xfec7, 0xcc5c, 0xddd5, 0xa96a, 0xb8e3, 0x8a78, 0x9bf1,
0x7387, 0x620e, 0x5095, 0x411c, 0x35a3, 0x242a, 0x16b1, 0x0738,
0xffcf, 0xee46, 0xdcdd, 0xcd54, 0xb9eb, 0xa862, 0x9af9, 0x8b70,
0x8408, 0x9581, 0xa71a, 0xb693, 0xc22c, 0xd3a5, 0xe13e, 0xf0b7,
0x0840, 0x19c9, 0x2b52, 0x3adb, 0x4e64, 0x5fed, 0x6d76, 0x7cff,
0x9489, 0x8500, 0xb79b, 0xa612, 0xd2ad, 0xc324, 0xf1bf, 0xe036,
0x18c1, 0x0948, 0x3bd3, 0x2a5a, 0x5ee5, 0x4f6c, 0x7df7, 0x6c7e,
0xa50a, 0xb483, 0x8618, 0x9791, 0xe32e, 0xf2a7, 0xc03c, 0xd1b5,
0x2942, 0x38cb, 0x0a50, 0x1bd9, 0x6f66, 0x7eef, 0x4c74, 0x5dfd,
0xb58b, 0xa402, 0x9699, 0x8710, 0xf3af, 0xe226, 0xd0bd, 0xc134,
0x39c3, 0x284a, 0x1ad1, 0x0b58, 0x7fe7, 0x6e6e, 0x5cf5, 0x4d7c,
0xc60c, 0xd785, 0xe51e, 0xf497, 0x8028, 0x91a1, 0xa33a, 0xb2b3,
0x4a44, 0x5bcd, 0x6956, 0x78df, 0x0c60, 0x1de9, 0x2f72, 0x3efb,
0xd68d, 0xc704, 0xf59f, 0xe416, 0x90a9, 0x8120, 0xb3bb, 0xa232,
0x5ac5, 0x4b4c, 0x79d7, 0x685e, 0x1ce1, 0x0d68, 0x3ff3, 0x2e7a,
0xe70e, 0xf687, 0xc41c, 0xd595, 0xa12a, 0xb0a3, 0x8238, 0x93b1,
0x6b46, 0x7acf, 0x4854, 0x59dd, 0x2d62, 0x3ceb, 0x0e70, 0x1ff9,
0xf78f, 0xe606, 0xd49d, 0xc514, 0xb1ab, 0xa022, 0x92b9, 0x8330,
0x7bc7, 0x6a4e, 0x58d5, 0x495c, 0x3de3, 0x2c6a, 0x1ef1, 0x0f78,

+ 18
- 0
lib/LibAPRS/CRC-CCIT.h View File

@@ -0,0 +1,18 @@
// CRC-CCIT Implementation based on work by Francesco Sacchi

#ifndef CRC_CCIT_H
#define CRC_CCIT_H

#include <stdint.h>
#include <avr/pgmspace.h>

#define CRC_CCIT_INIT_VAL ((uint16_t)0xFFFF)

extern const uint16_t crc_ccit_table[256];

inline uint16_t update_crc_ccit(uint8_t c, uint16_t prev_crc) {
return (prev_crc >> 8) ^ pgm_read_word(&crc_ccit_table[(prev_crc ^ c) & 0xff]);


+ 85
- 0
lib/LibAPRS/FIFO.h View File

@@ -0,0 +1,85 @@
#ifndef UTIL_FIFO_H
#define UTIL_FIFO_H

#include <stddef.h>
#include <util/atomic.h>

typedef struct FIFOBuffer
unsigned char *begin;
unsigned char *end;
unsigned char * volatile head;
unsigned char * volatile tail;
} FIFOBuffer;

inline bool fifo_isempty(const FIFOBuffer *f) {
return f->head == f->tail;

inline bool fifo_isfull(const FIFOBuffer *f) {
return ((f->head == f->begin) && (f->tail == f->end)) || (f->tail == f->head - 1);

inline void fifo_push(FIFOBuffer *f, unsigned char c) {
*(f->tail) = c;
if (f->tail == f->end) {
f->tail = f->begin;
} else {

inline unsigned char fifo_pop(FIFOBuffer *f) {
if(f->head == f->end) {
f->head = f->begin;
return *(f->end);
} else {
return *(f->head++);

inline void fifo_flush(FIFOBuffer *f) {
f->head = f->tail;

inline bool fifo_isempty_locked(const FIFOBuffer *f) {
bool result;
result = fifo_isempty(f);
return result;

inline bool fifo_isfull_locked(const FIFOBuffer *f) {
bool result;
result = fifo_isfull(f);
return result;

inline void fifo_push_locked(FIFOBuffer *f, unsigned char c) {
fifo_push(f, c);

inline unsigned char fifo_pop_locked(FIFOBuffer *f) {
unsigned char c;
c = fifo_pop(f);
return c;

inline void fifo_init(FIFOBuffer *f, unsigned char *buffer, size_t size) {
f->head = f->tail = f->begin = buffer;
f->end = buffer + size -1;

inline size_t fifo_len(FIFOBuffer *f) {
return f->end - f->begin;


+ 8
- 0
lib/LibAPRS/HDLC.h View File

@@ -0,0 +1,8 @@

#define HDLC_FLAG 0x7E
#define HDLC_RESET 0x7F
#define AX25_ESC 0x1B


+ 677
- 0
lib/LibAPRS/LICENSE View File

@@ -0,0 +1,677 @@
(This project uses BertOS for some functionality. BertOS is licensed under GPLv2. Please see for details. All files in the "bertos" directory originates from BertOS.)

Version 3, 29 June 2007

Copyright (C) 2007 Free Software Foundation, Inc. <>
Everyone is permitted to copy and distribute verbatim copies
of this license document, but changing it is not allowed.


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When we speak of free software, we are referring to freedom, not
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+ 348
- 0
lib/LibAPRS/LibAPRS.cpp View File

@@ -0,0 +1,348 @@
#include "Arduino.h"
#include "AFSK.h"
#include "AX25.h"

Afsk modem;
AX25Ctx AX25;
extern void aprs_msg_callback(struct AX25Msg *msg);
#define countof(a) sizeof(a)/sizeof(a[0])

int LibAPRS_vref = REF_3V3;
bool LibAPRS_open_squelch = false;

unsigned long custom_preamble = 350UL;
unsigned long custom_tail = 50UL;

AX25Call src;
AX25Call dst;
AX25Call path1;
AX25Call path2;

char CALL[7] = "NOCALL";
int CALL_SSID = 0;
char DST[7] = "APZMDM";
int DST_SSID = 0;
char PATH1[7] = "WIDE1";
int PATH1_SSID = 1;
char PATH2[7] = "WIDE2";
int PATH2_SSID = 2;

AX25Call path[4];

// Location packet assembly fields
char latitude[9];
char longtitude[10];
char symbolTable = '/';
char symbol = 'n';

uint8_t power = 10;
uint8_t height = 10;
uint8_t gain = 10;
uint8_t directivity = 10;

// Message packet assembly fields
char message_recip[7];
int message_recip_ssid = -1;

int message_seq = 0;
char lastMessage[67];
size_t lastMessageLen;
bool message_autoAck = false;

void APRS_init(int reference, bool open_squelch) {
LibAPRS_vref = reference;
LibAPRS_open_squelch = open_squelch;

ax25_init(&AX25, aprs_msg_callback);

void APRS_poll(void) {

void APRS_setCallsign(char *call, int ssid) {
memset(CALL, 0, 7);
int i = 0;
while (i < 6 && call[i] != 0) {
CALL[i] = call[i];
CALL_SSID = ssid;

void APRS_setDestination(char *call, int ssid) {
memset(DST, 0, 7);
int i = 0;
while (i < 6 && call[i] != 0) {
DST[i] = call[i];
DST_SSID = ssid;

void APRS_setPath1(char *call, int ssid) {
memset(PATH1, 0, 7);
int i = 0;
while (i < 6 && call[i] != 0) {
PATH1[i] = call[i];
PATH1_SSID = ssid;

void APRS_setPath2(char *call, int ssid) {
memset(PATH2, 0, 7);
int i = 0;
while (i < 6 && call[i] != 0) {
PATH2[i] = call[i];
PATH2_SSID = ssid;

void APRS_setMessageDestination(char *call, int ssid) {
memset(message_recip, 0, 7);
int i = 0;
while (i < 6 && call[i] != 0) {
message_recip[i] = call[i];
message_recip_ssid = ssid;

void APRS_setPreamble(unsigned long pre) {
custom_preamble = pre;

void APRS_setTail(unsigned long tail) {
custom_tail = tail;

void APRS_useAlternateSymbolTable(bool use) {
if (use) {
symbolTable = '\\';
} else {
symbolTable = '/';

void APRS_setSymbol(char sym) {
symbol = sym;

void APRS_setLat(char *lat) {
memset(latitude, 0, 9);
int i = 0;
while (i < 8 && lat[i] != 0) {
latitude[i] = lat[i];

void APRS_setLon(char *lon) {
memset(longtitude, 0, 10);
int i = 0;
while (i < 9 && lon[i] != 0) {
longtitude[i] = lon[i];

void APRS_setPower(int s) {
if (s >= 0 && s < 10) {
power = s;

void APRS_setHeight(int s) {
if (s >= 0 && s < 10) {
height = s;

void APRS_setGain(int s) {
if (s >= 0 && s < 10) {
gain = s;

void APRS_setDirectivity(int s) {
if (s >= 0 && s < 10) {
directivity = s;

void APRS_printSettings() {
Serial.println(F("LibAPRS Settings:"));
Serial.print(F("Callsign: ")); Serial.print(CALL); Serial.print(F("-")); Serial.println(CALL_SSID);
Serial.print(F("Destination: ")); Serial.print(DST); Serial.print(F("-")); Serial.println(DST_SSID);
Serial.print(F("Path1: ")); Serial.print(PATH1); Serial.print(F("-")); Serial.println(PATH1_SSID);
Serial.print(F("Path2: ")); Serial.print(PATH2); Serial.print(F("-")); Serial.println(PATH2_SSID);
Serial.print(F("Message dst: ")); if (message_recip[0] == 0) { Serial.println(F("N/A")); } else { Serial.print(message_recip); Serial.print(F("-")); Serial.println(message_recip_ssid); }
Serial.print(F("TX Preamble: ")); Serial.println(custom_preamble);
Serial.print(F("TX Tail: ")); Serial.println(custom_tail);
Serial.print(F("Symbol table: ")); if (symbolTable = '/') { Serial.println(F("Normal")); } else { Serial.println(F("Alternate")); }
Serial.print(F("Symbol: ")); Serial.println(symbol);
Serial.print(F("Power: ")); if (power < 10) { Serial.println(power); } else { Serial.println(F("N/A")); }
Serial.print(F("Height: ")); if (height < 10) { Serial.println(height); } else { Serial.println(F("N/A")); }
Serial.print(F("Gain: ")); if (gain < 10) { Serial.println(gain); } else { Serial.println(F("N/A")); }
Serial.print(F("Directivity: ")); if (directivity < 10) { Serial.println(directivity); } else { Serial.println(F("N/A")); }
Serial.print(F("Latitude: ")); if (latitude[0] != 0) { Serial.println(latitude); } else { Serial.println(F("N/A")); }
Serial.print(F("Longtitude: ")); if (longtitude[0] != 0) { Serial.println(longtitude); } else { Serial.println(F("N/A")); }

void APRS_sendPkt(void *_buffer, size_t length) {

uint8_t *buffer = (uint8_t *)_buffer;

memcpy(, DST, 6);
dst.ssid = DST_SSID;

memcpy(, CALL, 6);
src.ssid = CALL_SSID;

memcpy(, PATH1, 6);
path1.ssid = PATH1_SSID;

memcpy(, PATH2, 6);
path2.ssid = PATH2_SSID;

path[0] = dst;
path[1] = src;
path[2] = path1;
path[3] = path2;

ax25_sendVia(&AX25, path, countof(path), buffer, length);

// Dynamic RAM usage of this function is 30 bytes
void APRS_sendLoc(void *_buffer, size_t length) {
size_t payloadLength = 20+length;
bool usePHG = false;
if (power < 10 && height < 10 && gain < 10 && directivity < 9) {
usePHG = true;
payloadLength += 7;
uint8_t *packet = (uint8_t*)malloc(payloadLength);
uint8_t *ptr = packet;
packet[0] = '=';
packet[9] = symbolTable;
packet[19] = symbol;
memcpy(ptr, latitude, 8);
ptr += 9;
memcpy(ptr, longtitude, 9);
ptr += 10;
if (usePHG) {
packet[20] = 'P';
packet[21] = 'H';
packet[22] = 'G';
packet[23] = power+48;
packet[24] = height+48;
packet[25] = gain+48;
packet[26] = directivity+48;
if (length > 0) {
uint8_t *buffer = (uint8_t *)_buffer;
memcpy(ptr, buffer, length);

APRS_sendPkt(packet, payloadLength);

// Dynamic RAM usage of this function is 18 bytes
void APRS_sendMsg(void *_buffer, size_t length) {
if (length > 67) length = 67;
size_t payloadLength = 11+length+4;

uint8_t *packet = (uint8_t*)malloc(payloadLength);
uint8_t *ptr = packet;
packet[0] = ':';
int callSize = 6;
int count = 0;
while (callSize--) {
if (message_recip[count] != 0) {
packet[1+count] = message_recip[count];
if (message_recip_ssid != -1) {
packet[1+count] = '-'; count++;
if (message_recip_ssid < 10) {
packet[1+count] = message_recip_ssid+48; count++;
} else {
packet[1+count] = 49; count++;
packet[1+count] = message_recip_ssid-10+48; count++;
while (count < 9) {
packet[1+count] = ' '; count++;
packet[1+count] = ':';
ptr += 11;
if (length > 0) {
uint8_t *buffer = (uint8_t *)_buffer;
memcpy(ptr, buffer, length);
memcpy(lastMessage, buffer, length);
lastMessageLen = length;

if (message_seq > 999) message_seq = 0;

packet[11+length] = '{';
int n = message_seq % 10;
int d = ((message_seq % 100) - n)/10;
int h = (message_seq - d - n) / 100;

packet[12+length] = h+48;
packet[13+length] = d+48;
packet[14+length] = n+48;
APRS_sendPkt(packet, payloadLength);

void APRS_msgRetry() {
APRS_sendMsg(lastMessage, lastMessageLen);

// For getting free memory, from:

extern unsigned int __heap_start;
extern void *__brkval;

struct __freelist {
size_t sz;
struct __freelist *nx;

extern struct __freelist *__flp;

int freeListSize() {
struct __freelist* current;
int total = 0;
for (current = __flp; current; current = current->nx) {
total += 2; /* Add two bytes for the memory block's header */
total += (int) current->sz;
return total;

int freeMemory() {
int free_memory;
if ((int)__brkval == 0) {
free_memory = ((int)&free_memory) - ((int)&__heap_start);
} else {
free_memory = ((int)&free_memory) - ((int)__brkval);
free_memory += freeListSize();
return free_memory;

+ 39
- 0
lib/LibAPRS/LibAPRS.h View File

@@ -0,0 +1,39 @@
#include "Arduino.h"
#include <stdint.h>
#include <stdbool.h>

#include "FIFO.h"
#include "CRC-CCIT.h"
#include "HDLC.h"
#include "AFSK.h"
#include "AX25.h"

void APRS_init(int reference, bool open_squelch);
void APRS_poll(void);

void APRS_setCallsign(char *call, int ssid);
void APRS_setDestination(char *call, int ssid);
void APRS_setMessageDestination(char *call, int ssid);
void APRS_setPath1(char *call, int ssid);
void APRS_setPath2(char *call, int ssid);

void APRS_setPreamble(unsigned long pre);
void APRS_setTail(unsigned long tail);
void APRS_useAlternateSymbolTable(bool use);
void APRS_setSymbol(char sym);

void APRS_setLat(char *lat);
void APRS_setLon(char *lon);