I have found what caused the problem, but have no idea why it does so.
As I mentioned earlier, the units supports two types of RF units. One type just reads the data. The other type requests data from different types of sensors on a single wire (so they can be chained).
To avoid the need to select the type manually, I implemented auto detection by first reading the signal pin (12). If I get some data within 1 second, it will support the requesting type (type-X). If not it will support the other type (type-D). This is done in isTelemetryTypeX().
The problem seems to be that SoftwareSerial gets upset if I read pin 12 first, and later use it to transmit data:
SoftwareSerial serialD(PIN_SerialTelemetryRX, PIN_SerialTelemetryTX, true);
SoftwareSerial telemetryTypeCheck(PIN_SerialTelemetryTX, PIN_SerialTelemetryRX, true); // Get input from Tx pin
The really strange part is that, as mentioned in previous posts, there is no problem if the pin transmits data to HW serial (setup #2), only if it transmits to SoftwareSerial on the other Pro Mini (setup #4). Data never gets available() there.
If I use another pin for SoftwareSerial telemetryTypeCheck(), the call to isTelemetryTypeX() causes no problems, but obviously becomes useless.
Anyone have an idea why this happens?
/*
Author: flarssen, 05/2015
GPS to FrSky Telemetry interface,
using
FrSky S-Port Telemetry library http://www.rcgroups.com/forums/showthread.php?t=2245978
TinyGPS library http://arduiniana.org/libraries/tinygps/
*/
#include <SoftwareSerial.h>
#include <TinyGPS.h>
#include "FrSkySportSensor.h"
#include "FrSkySportSensorGps.h"
#include "FrSkySportSingleWireSerial.h"
#include "FrSkySportTelemetry.h"
#define LED_PIN 13 // the pin connected to onboard LED
#define PIN_SerialTelemetryRX 255 // dummy
#define PIN_SerialTelemetryTX 12 // the pin to use for serial data to the FrSky receiver
FrSkySportSensorGps gps; // GPS sensor
FrSkySportTelemetry telemetry; // Telemetry object
TinyGPS tinyGps;
SoftwareSerial serialD(PIN_SerialTelemetryRX, PIN_SerialTelemetryTX, true);
SoftwareSerial telemetryTypeCheck(PIN_SerialTelemetryTX, PIN_SerialTelemetryRX, true); // Get input from Tx pin
uint32_t currentTime, sentenceTime1, sentenceTime2;
boolean telemetryTypeX;
byte gpsSentences = 0;
byte X[] = {3,1,1,3,0}; // -..-
byte D[] = {3,1,1,0}; // -..
void morse(byte values[])
{
for(int i=0; values[i]; i++) {
digitalWrite(LED_PIN, HIGH);
delay(values[i]*100);
digitalWrite(LED_PIN, LOW);
delay(100);
}
delay(300);
}
boolean isTelemetryTypeX(void) {
unsigned long lastTime;
boolean x = false;
telemetryTypeCheck.begin(115200);
lastTime = millis();
while (millis() < lastTime + 1000) {
while (telemetryTypeCheck.available()) {
if(telemetryTypeCheck.read() == FRSKY_TELEMETRY_START_FRAME) {
x = true;
break;
}
}
}
telemetryTypeCheck.end();
return x;
}
void SendDValue(uint8_t ID, uint16_t Value) {
uint8_t lsb = Value & 0x00ff;
uint8_t msb = (Value & 0xff00)>>8;
serialD.write(0x5E);
serialD.write(ID);
if(lsb == 0x5E) {
serialD.write(0x5D);
serialD.write(0x3E);
}
else if(lsb == 0x5D) {
serialD.write(0x5D);
serialD.write(0x3D);
}
else {
serialD.write(lsb);
}
if(msb == 0x5E) {
serialD.write(0x5D);
serialD.write(0x3E);
}
else if(msb == 0x5D) {
serialD.write(0x5D);
serialD.write(0x3D);
}
else {
serialD.write(msb);
}
serialD.write(0x5E);
}
void SendDGpsData(void) {
float flat, flon, falt, fc, fk, fmins;
unsigned long fix_age;
uint16_t degr, mins;
tinyGps.f_get_position(&flat, &flon, &fix_age);
falt = tinyGps.f_altitude(); // +/- altitude in meters
fc = tinyGps.f_course(); // course in degrees
fk = tinyGps.f_speed_mps(); // speed in m/sec
degr = (uint16_t)flat;
fmins = (flat-degr)*60;
mins = (uint16_t)fmins;
SendDValue(0x13, degr*100+(uint16_t)fmins); // Latitude (DDMM)
SendDValue(0x1B, (uint16_t)((fmins-mins)*10000)); // Latitude (.MMMM)
SendDValue(0x23, (uint16_t)(flat < 0 ? 'S' : 'N'));
degr = (uint16_t)flon;
fmins = (flon-degr)*60;
mins = (uint16_t)fmins;
SendDValue(0x12, degr*100+(uint16_t)fmins); // Longitude (DDMM)
SendDValue(0x1A, (uint16_t)((fmins-mins)*10000)); // Longitude (.MMMM)
SendDValue(0x22, (uint16_t)(flon < 0 ? 'W' : 'E'));
SendDValue(0x01, (int16_t)falt); // Altitude m
SendDValue(0x09, (uint16_t)((abs(falt)-(uint16_t)abs(falt))*100)); // Altitude centimeter
SendDValue(0x11, (uint16_t)fk); // Speed knots
SendDValue(0x19, (uint16_t)((fk-(uint16_t)fk)*100)); // Speed decimals
SendDValue(0x14, (uint16_t)fc); // Course degrees
SendDValue(0x1C, (uint16_t)((fc-(uint16_t)fc)*100)); // Course decimals
}
void SetXGpsData(void)
{
float flat, flon, falt, fc, fmps;
unsigned long fix_age;
tinyGps.f_get_position(&flat, &flon, &fix_age);
falt = tinyGps.f_altitude(); // +/- altitude in meters
fc = tinyGps.f_course(); // course in degrees
fmps = tinyGps.f_speed_mps(); // speed in m/sec
gps.setData(flat, flon, falt, fmps, fc, 14, 9, 14, 12, 00, 00);
}
void setup()
{
pinMode(LED_PIN, OUTPUT);
telemetryTypeX = isTelemetryTypeX();
if (telemetryTypeX) {
telemetry.begin(FrSkySportSingleWireSerial::SOFT_SERIAL_PIN_12, &gps);
morse(X);
}
else {
serialD.begin(9600);
morse(D);
}
Serial.begin(9600);
}
void loop() {
while (Serial.available() > 0) {
if (tinyGps.encode(Serial.read())) { // if a NMEA sentence is complete
if (!gpsSentences) // if first of two sentences
sentenceTime1 = millis(); // timestamp sentence 1
else
sentenceTime2 = millis(); // timestamp sentence 2
gpsSentences++;
}
if (gpsSentences > 1) { // if more then one sentence
if (sentenceTime2 - sentenceTime1 > 175) {// sentences not from same dataset, resync
sentenceTime1 = sentenceTime2;
gpsSentences = 1;
}
else { // process GPS data
digitalWrite(LED_PIN, HIGH);
if (telemetryTypeX)
SetXGpsData();
else
SendDGpsData();
digitalWrite(LED_PIN, LOW);
gpsSentences = 0;
}
}
}
if (telemetryTypeX)
telemetry.send();
}
Fred
With the addition of a handshake line, the Master (with the sensor) could "request" data from the Slave (with the GPS)... at the right time. Because the Master has to service the sensor every 125ms, it knows when those Serial interrupts will mess up the SoftwareSerial transfer with the Slave.
