PI 3 to Arduino UART serial comms - Raspberry Pi Forums

hello all,

once again looking collective knowledge of forum solution problem.

communicating between raspberry pi (python 3.4) , arduino uno, or should say, trying.

here should happen....

send command string arduino "f25000,3500" new line character. uno reads byte-by-byte , echos pi. arduino processes data further , waits new command.

works first time (first run on pi's program, , boot on arduino. if re-run program on , on again, works fine.

however, when pi sends 2 or more commands uno things strange. instead of sending command - sends odd characters, possibly more should. earlier, first command fine, second, third , on commands turn jiberish.

first command working, seems though goes on between commands messes serial data.

things have noticed
on first communication, send 12 bytes , 12 bytes (not counting lf)
checking buffer amount 12 on first command
data being echoed uno identical data sent
on second communication, send 12 byte , 18 bytes back
checking buffer amount 18 on second command
data being echoed uno jiberish


have tried many different things no avail, however...
assuming had serial port , perhaps buffer data on pi side...
tried flushing buffers - didn't help.
tried opening port - sending data - closing port repeating - didn't help.
running without uno serial port monitor active - didn't help.
running without uno connected usb on computer (power adapter instead - no help.


suspect problem on pi side have not been able pinpoint issue.


sure hope can me out on one.

in advance,
chris d

python 3.4 code

code: select all

# routine send command arduino , execute # cannot repeatedly within loop  time import sleep import serial import binascii  err_cnt = 0  #start code open serial port ser = serial.serial("/dev/ttys0",9600, timeout =1) print("hello, waiting data...") if ser.isopen():     print(ser.name, "is open")     print(ser)     # create & send command arduino def send_command_to_pi(command_string, steps, sps):     global err_cnt     command_string = command_string     ser.write(command_string.encode('ascii'))     sleep(.2)     val1 = steps + ","     ser.write(val1.encode('ascii'))     sleep(.2)     val2 = sps     check_val = command_string + val1 + val2     val2 = val2 + "\n"     ser.write(val2.encode('ascii'))     print("sent")      sleep(.1)     buffer = ser.inwaiting()     print("buffer ",buffer)      try:         indata = bytes.decode(ser.read())         indata = indata + bytes.decode(ser.read())         indata = indata + bytes.decode(ser.read())              indata = indata + bytes.decode(ser.read())              indata = indata + bytes.decode(ser.read())              indata = indata + bytes.decode(ser.read())              indata = indata + bytes.decode(ser.read())              indata = indata + bytes.decode(ser.read())              indata = indata + bytes.decode(ser.read())              indata = indata + bytes.decode(ser.read())              indata = indata + bytes.decode(ser.read())          indata = indata + bytes.decode(ser.read())              indata = indata + bytes.decode(ser.read())              indata = indata + bytes.decode(ser.read())              indata = indata + bytes.decode(ser.read())              indata = indata + bytes.decode(ser.read())           print("s",check_val)         print("r",indata)         print("cmds ",x, "   errors ",err_cnt)     except:         err_cnt += 1         print("error count =",err_cnt)         sleep(1)    #first command sent arduino print("------------------------") command_string = "f" steps = "25000" sps = "3500" send_command_to_pi(command_string, steps, sps)  #wait long enough activity done on arduino sleep(20)  #second command sent arduino print("------------------------") command_string = "r" steps = "25000" sps = "3500" send_command_to_pi(command_string, steps, sps) 

arduino code (only relevant sections)

code: select all

 ...   serial.begin(9600);           // set serial library @ 9600 bps ...    // fetch commands serial port if there   if (serial.available() > 0) {     inbyte = serial.read();     if (inbyte != 10 || inbyte != 13)      {       serial.write(inbyte); // echo pi sent in command     }          // input if letter, number, =,?,+ typed!     if ((inbyte >= 65 && inbyte <= 90) || (inbyte >= 97 && inbyte <= 122) || (inbyte >= 48 &&     inbyte <= 57) || inbyte == 44 || inbyte == 61 || inbyte == 63) {       serial_command.concat(inbyte);     }// end serial.available     // process command when nl/cr entered:      // handle incomming commands raspberry pi     if (inbyte == 10 || inbyte == 13) {       inbyte = 0;       // respond command:       if (serial_command.startswith("f")) //forward motion command       {         temp1 = serial_command.substring(1, serial_command.indexof(','));         temp2 = serial_command.substring(serial_command.indexof(',') + 1);         temp1.tochararray(carray, 10);         cmd_steps = atol(carray);         temp2.tochararray(carray, 10);         target_sps = atol(carray);         digitalwrite(leftwheeldir,l_fwd);         digitalwrite(rightwheeldir,r_fwd);         end_move_alert = 1;         steps = 0;         target_steps = cmd_steps;         steps_to_go = cmd_steps;         acc_flag = 1;         command = 0;         //response pi         //serial.println(command);         //serial.println(cmd_steps);         //serial.println(target_sps);       }       else if (serial_command.startswith("r")) // reverse motion command       {         temp1 = serial_command.substring(1, serial_command.indexof(','));         temp2 = serial_command.substring(serial_command.indexof(',') + 1);         temp1.tochararray(carray, 10);         cmd_steps = atol(carray);         temp2.tochararray(carray, 10);         target_sps = atol(carray);         digitalwrite(leftwheeldir,l_rev);         digitalwrite(rightwheeldir,r_rev);         end_move_alert = 1;         steps = 0;         target_steps = cmd_steps;         steps_to_go = cmd_steps;         acc_flag = 1;         command = 1;         //response pi         //serial.println(command);         //serial.println(cmd_steps);         //serial.println(target_sps);       else        {         if (!serial_command.equalsignorecase(""))          {           //serial.println("bad");         }        }        serial_command = "";     }   }      }// end main loop   

are uart both running @ same voltage level? iirc, pi 3.3v, arduino 5v. might issue there.

raspberrypi