Data reading from RS485 Interface Particle Matter sensor

Hello,

Am working on Particle matter sensor which works on RS485 Interface protocol.

To read the data from the sensor, Command format: aR0

With Arduino Uno, but unable to read the data, as always it prints -1 and 0 on the serial monitor.
I have tried the below three types, each one declaration as the command format. But nothing works.

#define reqn ‘a’
int reqn = 0x61;
char reqn = “aR0”;

What am doing wrong in the attached code?? Also attached the sensor technical literature.

Your reply will be appreciated.

FRT RDM EN.pdf (1.24 MB)

sketch_RDM200.ino (2.51 KB)

int byteReceived;
int byteSend;

It is stupid to use a type in a name, when the type is NOT the type of the variable. The type in the name is correct. The type OF the variables is wrong!

Since the command format is “aR0”, one would think that using a function that sends one byte of data in binary format would just not cut the mustard.

Try RS485Serial.print(“aR0”);