// ---------------------------------------------------------------------------------------
// Acurite 00606TX Reader
// Adapted from code by Ray Wang (Rayshobby LLC)
// ---------------------------------------------------------------------------------------
#define DATAPIN D2
// ring buffer size has to be large enough to fit
// data between two successive sync signals
#define RING_BUFFER_SIZE 256
#define SYNC_LENGTH 9000
#define SEP_LENGTH 500
#define BIT1_LENGTH 4000
#define BIT0_LENGTH 2000
#define MESSAGE_SIZE 32
#define LSFR_OFFSET 4
uint8_t LSFR_sequence[MESSAGE_SIZE] = {0};
//ringbuffer contains the time since the last signal was off.
unsigned long timings[RING_BUFFER_SIZE];
unsigned int syncIndex1 = 0; // index of the first sync signal
unsigned int syncIndex2 = 0; // index of the second sync signal
bool received = false;
//protypes
void ICACHE_RAM_ATTR handler();
// ---------------------------------------------------------------------------------------
// setup
// ---------------------------------------------------------------------------------------
void setup() {
Serial.begin(115200);
pinMode(DATAPIN, INPUT);
attachInterrupt(digitalPinToInterrupt(DATAPIN), handler, CHANGE);
Serial.println("\n\nStarted");
}
// ---------------------------------------------------------------------------------------
// loop
// ---------------------------------------------------------------------------------------
void loop() {
//Did we get a message?
if (received == true) {
Serial.println("\nReceived...");
// disable interrupt to avoid new data corrupting the buffer
detachInterrupt(digitalPinToInterrupt(DATAPIN));
//processSignal
unsigned int bits[34];
bool error = processSignal(bits);
if(error==false){
//convert our bits to byte array
byte data[4];
bool success = bitsToByteArray(bits,32,data,4);
if(success){
byte rollingCode = data[0];
Serial.printf("Rolling Code: 0x%02x\n",rollingCode);
byte batteryStatus = (data[1] & 0xf0) >> 4;
Serial.printf("Battery Status: 0x%02x\n",batteryStatus);
float temperature = computeTemperature(data[1],data[2]);
Serial.printf("Temp: %0.1f C\n",temperature);
byte checksum = data[3];
Serial.printf("checksum: 0x%02x\n",checksum);
//uint8_t computeChecksum(int length, uint8_t *buff) {
byte computedChecksum = computeChecksum(3,data);
if(checksum==computedChecksum){
Serial.printf("Checksum Verified!\n");
}else{
Serial.printf("Checksum Invalid!\n");
}
}else{
Serial.printf("Failed to convert bits to bytes array\n");
}
}//if(error==false){
// delay for 1 second to avoid repetitions
delay(1000);
received = false;
syncIndex1 = 0;
syncIndex2 = 0;
// re-enable interrupt
attachInterrupt(digitalPinToInterrupt(DATAPIN), handler, CHANGE);
}//if (received == true) {
}
// ---------------------------------------------------------------------------------------
// computeTemperature
// ---------------------------------------------------------------------------------------
// Temperature is a signed 12-bit value with resolution of 0.1C. For example,
// 25.6C is encoded as the value 256 (0x100 hexadecimal). A value of -0.1C is
// encoded as -1 (0xFFF hexadecimal).
// ---------------------------------------------------------------------------------------
float computeTemperature(byte highbyte, byte lowbyte){
bool negative=false;
Serial.printf("highbyte : 0x%02x \n",highbyte);
if((highbyte & 0x08) == 0x08){
negative=true;
Serial.println("Negative");
}
int rawTemperature = ((highbyte & 0x0f) << 8) + lowbyte;
Serial.printf("rawTemperature: %d\n",rawTemperature);
if(negative){
rawTemperature = rawTemperature - 4096;
//limit to -40C like the acurite receiver
if(rawTemperature < -400){
rawTemperature = -400;
}
}
float temperature = rawTemperature / 10.0;
return temperature;
}
// ---------------------------------------------------------------------------------------
// processSignal
// ---------------------------------------------------------------------------------------
// Message is composed of:
// - Rolling Code(2 nibbles - 8 bits),
// - Status(1 nibble - 4 bits),
// - Temperature (signed binary - 3 nibbles - 12 bits ),
// - Hash Code (2 nibles - 8 bits)
//
// Each bit is composed of two signals - a seperator signal followed by a short/long
// ---------------------------------------------------------------------------------------
bool processSignal(unsigned int *bits){
bool error = false;
int totalSignalsInMessage = 32 *2;
int count =0;
for(unsigned int i=syncIndex1; i!=(syncIndex1+totalSignalsInMessage)%RING_BUFFER_SIZE; i=(i+2)%RING_BUFFER_SIZE) {
unsigned long t0 = timings[i];
unsigned long t1 = timings[(i+1)%RING_BUFFER_SIZE];
if (t0>(SEP_LENGTH-150) && t0<(SEP_LENGTH+150)){
if (t1>(BIT1_LENGTH-1000) && t1<(BIT1_LENGTH+1000)) {
bits[count]=1;
} else if (t1>(BIT0_LENGTH-1000) && t1<(BIT0_LENGTH+1000)) {
bits[count]=0;
} else {
bits[count]=-1;
}
}else {
// Serial.printf("** t0: %d, t1: %d\n",t0,t1);
// Serial.printf("Read Error\n");
error=true;
break;
}
count++;
}//for
if(error==false){
//print bits received
Serial.print("bits: ");
for(int i=0;i<32;i++){
if(bits[i]>=0){
Serial.print(bits[i]);
}else{
Serial.print("X");
}
if((i+1)%4==0){
Serial.printf(" ");
}
}
Serial.println("");
}
return error;
}
// ---------------------------------------------------------------------------------------
// isSync
// ---------------------------------------------------------------------------------------
// Detect if a sync signal is present. A sync signal is composed of a seperator signal
// (short off 0.5ms) followed by a sync signal (9ms off).
// ---------------------------------------------------------------------------------------
bool isSync(unsigned int idx) {
//get the last two indexes from the ring buffer
int t0Index = (idx+RING_BUFFER_SIZE-1) % RING_BUFFER_SIZE;
unsigned long t0 = timings[t0Index];
unsigned long t1 = timings[idx];
//check that t0 is a seperator signal, should be around 0.5ms
if (t0>(SEP_LENGTH-100) && t0<(SEP_LENGTH+100) ){
//check that t1 is a sync signal, allow for anything between 8-10ms
if (t1>(SYNC_LENGTH-1000) && t1<(SYNC_LENGTH+1000)){
if (digitalRead(DATAPIN) == HIGH) {
// Serial.printf("toIndex=%d, idx=%d, RING_BUFFER_SIZE=%d \n",t0Index, idx, RING_BUFFER_SIZE);
// Serial.printf("t0=%d, t1=%d\n",t0,t1);
//found
return true;
}
}
}
return false;
}
// ---------------------------------------------------------------------------------------
// handler
// ---------------------------------------------------------------------------------------
// Interrupt handler - reads incoming signal changes from receiver
// ---------------------------------------------------------------------------------------
void ICACHE_RAM_ATTR handler() {
static unsigned long duration = 0;
static unsigned long lastTime = 0;
static unsigned int ringIndex = 0;
static unsigned int syncCount = 0;
// exit out if we are in processing a signal.
if (received == true) {
// Serial.println("received==true");
return;
}
// calculating timing since last change
long time = micros();
duration = time - lastTime;
lastTime = time;
// store data in ring buffer
ringIndex = (ringIndex + 1) % RING_BUFFER_SIZE;
timings[ringIndex] = duration;
// detect sync signal
if (isSync(ringIndex)) {
syncCount ++;
if (syncCount == 1) {
// first time sync is seen, record buffer index
syncIndex1 = (ringIndex+1) % RING_BUFFER_SIZE;
}else if (syncCount == 2) {
syncCount = 0;
// second time sync is seen, start bit conversion
syncIndex2 = (ringIndex+1) % RING_BUFFER_SIZE;
//check how many signals we have received between syncs
unsigned int changeCount = 0;
if(syncIndex2 < syncIndex1){
changeCount = syncIndex2+RING_BUFFER_SIZE - syncIndex1;
}else{
changeCount = syncIndex2 - syncIndex1;
}
if (changeCount < 66 || changeCount > 68) {
//too many signals, disregard
received = false;
syncIndex1 = 0;
syncIndex2 = 0;
} else {
//we found our signal
received = true;
}
}
}
}
// ---------------------------------------------------------------------------------------
// calculateLSFR
// ---------------------------------------------------------------------------------------
void calculateLSFR() {
int i;
uint8_t reg = 0x7C;
uint8_t temp_reg = 0;
for (i = 0; i < MESSAGE_SIZE; i++) {
temp_reg = reg & 0x01;
reg >>= 1;
reg |= (temp_reg << 7);
if (temp_reg) {
reg ^= 0x18;
}
LSFR_sequence[i] = reg;
//printf("%02x\n", LSFR_sequence[i]);
}
}
// ---------------------------------------------------------------------------------------
// combineLSFR
// ---------------------------------------------------------------------------------------
uint8_t combineLSFR(uint8_t len, uint8_t *data) {
uint8_t hash_reg = 0; // not 0x64
int byte_idx, bit_idx;
uint8_t byte, bit;
//printf("***COMBINE\n");
for (byte_idx = 0; byte_idx < len; byte_idx++) {
for (bit_idx = 7; bit_idx >= 0; bit_idx--) {
bit = (data[byte_idx] & (1 << bit_idx)) >> bit_idx;
if (bit) {
hash_reg ^= LSFR_sequence[byte_idx * 8 + (7 - bit_idx) + LSFR_OFFSET];
//printf("[%d]: %02x\n", byte_idx * 8 + (7 - bit_idx), hash_reg);
}
bit = 0;
}
}
return hash_reg;
}
// ---------------------------------------------------------------------------------------
// computeChecksum
// ---------------------------------------------------------------------------------------
uint8_t computeChecksum(int length, uint8_t *buff) {
calculateLSFR();
return combineLSFR(length, buff);
}
// ---------------------------------------------------------------------------------------
// bitsToByteArray
// ---------------------------------------------------------------------------------------
// Convert array of integers containing the bits received into byte array
// ---------------------------------------------------------------------------------------
bool bitsToByteArray(unsigned int *bits, int len, byte* buffer, int bufferLen){
int bidx=0;
unsigned int sum = 0;
for(int i=0;i<len;i++){
//break out if we have filled up the buffer
if(bidx >= bufferLen){
return false;
}
sum += bits[i];
//new byte?
if((i+1)%8==0){
//save to buffer, reset sum and increment bidx
buffer[bidx]=sum;
sum=0;
bidx++;
}else{
sum<<=1;
}
}
return true;
} |