5 years, 1 month ago.

Delayed PC output Python/RPC

I'm a relative beginner so any help is much appreciated.

I am running RPC over Serial and interfacing with python. Currently, I have an RPCFunction set up to pass a string from my PC to the mbed. There should be multiple prints when the function runs as I am trying to debug but they seem to get backed up and print one message every time I run the function. The output will be more clear than me explaining.

mbed code

#include "mbed.h"
#include "mbed_rpc.h"
#include <string>
#include <iostream>

using namespace std;

Serial pc(USBTX, USBRX);

string msg("TEST: ");

void DoEcho(Arguments* input, Reply* output);
RPCFunction Echo(&DoEcho, "Echo");

void DoEcho(Arguments* input, Reply* output) {
    msg += input->argv[0];
    pc.printf("DoEcho: %s\n", msg);

int main() {

    // receive commands, and send back the responses
    char buf[256], outbuf[256];
    while(1) {
        pc.gets(buf, 256);
        //Call the static call method on the RPC class
        RPC::call(buf, outbuf);
        pc.printf("OUTPUT: %s\n", outbuf);

Python on PC

$ python
>>> from mbedRPC import *
>>> serdev = "/dev/ttyACM0"
>>> mbed = SerialRPC(serdev, 9600)
>>> echo = RPCFunction(mbed, "Echo")
>>> echo.run("Ant")
>>> echo.run("Eat")
'DoEcho: TEST: Eat'
>>> echo.run("Tree")
>>> echo.run("Cow")
'DoEcho: TEST: EatTree'
>>> echo.run("Sand")
'OUTPUT: Tree'
>>> echo.run("Burger")
'DoEcho: TEST: EatTreeCow'


My end goal is to pass a string from the pc to the mbed, then relay it to another mbed via i2c. I can do both of these things separately but when I combine both the i2c handling and RPC in the main things have fallen apart. I was using these prints to debug that issue but they were not helpful when they did not display.

Question relating to:

It appears that this was an issue with the "\n" in printf. Removing this allowed me to get all output I was expecting.

posted by Mark Engstrom 07 Oct 2015
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