Hi, I've spent some days trying to get a SDS011 (Particulate matter sensor) and a GPS work on the same board.
This morning I've found the source of the error but I don't seem to find a solution.
The issue is that both device rely on SoftwareSerial and only one serial port can be read at once. Usually the solution seems to be to use the listen() command from the SoftwareSerial Package.
I therefore dowloaded the SDS011 library with selectable serial port (found here), but is this library conpatible with the use i have? or is it only for "Hardware serial"?. (The package i used to get data from the GPS is the TinyGps library.)
Here is what my "Debugging" tells me:
- if only the SDS011 is read using the listen() command (no 'listen()' used for the GPS), the SDS011 successfully outputs data at 1Hz
- If attempting to read from the two sensors at the same time, The GPS unis always seem to be able to successfully retrieve data
- Accessing the GPS first or the SDS011 doesn't change the output: GPS always works while the SDS fails.
To sum up, if the SDS011 is the only device with a serial.listen() there are no issues, as soon as I add the ss.listen() for the GPS, the SDS fails to retrieve data, although the corresponding 'isListening()' statement returns as true! (Am I looking at the wrong problem then??)
Thanks a lot for the time you might have spent reading this post, hope the issue is clear.
I'ts my first post ever on a forum, so I'm sorry if I made formatting errors or if I didn't post in the correct thread!
P.S. I've looked at ohter posts on the forum, (this one for example) butfailed to find a solution.
#include <SoftwareSerial.h>
#include <TinyGPS.h>
//#include <SDS011.h>
#include <SDS011-select-serial.h>
float p10, p25;
int error;
TinyGPS gps;
SoftwareSerial ss(10, 9);// Serial initialisation for the GPS
SoftwareSerial SDS_Serial(11, 8);// Serial initilaisation for the SDS011 (Checked, Correct port used)
SDS011 my_sds(SDS_Serial);
void setup()
{
Serial.begin(115200);
ss.begin(9600);
SDS_Serial.begin(9600); // Initialising SDS011 Serial
}
void loop()
{
bool newData = false;
unsigned long chars;
unsigned short sentences, failed;
//****************************** Reading SDS011 ******************************
SDS_Serial.listen(); //Listen to the SDS Serial
if (! SDS_Serial.isListening()){
Serial.println("No SDS serial connection");
}
error = my_sds.read(&p25,&p10);
if (! error) {
Serial.print( String(p10)+"\t"+String(p25)+"\n");
}
else
{
Serial.print("\t SDS011 Not readable\n ");
}
//****************************** END SDS011 ******************************
ss.listen();
if (! ss.isListening()){
Serial.println(" No GPS Serial");
}
// For one second we parse GPS data and report some key values
for (unsigned long start = millis(); millis() - start < 1000;)
{
while (ss.available())
{
char c = ss.read();
Serial.write(c); // uncomment this line if you want to see the GPS data flowing
if (gps.encode(c)) // Did a new valid sentence come in?
newData = true;
}
}
if (newData)
{
float flat, flon;
unsigned long age;
gps.f_get_position(&flat, &flon, &age);
Serial.print("LAT=");
Serial.print(flat == TinyGPS::GPS_INVALID_F_ANGLE ? 0.0 : flat, 6);
Serial.print(" LON=");
Serial.print(flon == TinyGPS::GPS_INVALID_F_ANGLE ? 0.0 : flon, 6);
Serial.print(" SAT=");
Serial.print(gps.satellites() == TinyGPS::GPS_INVALID_SATELLITES ? 0 : gps.satellites());
Serial.print(" PREC=");
Serial.print(gps.hdop() == TinyGPS::GPS_INVALID_HDOP ? 0 : gps.hdop());
}
gps.stats(&chars, &sentences, &failed);
Serial.print(" CHARS=");
Serial.print(chars);
Serial.print(" SENTENCES=");
Serial.print(sentences);
Serial.print(" CSUM ERR=");
Serial.print(failed);
if (chars == 0)
Serial.println("** No characters received from GPS: check wiring **");
delay(1000);
}
