Edit - Stack Overflow

You are not logged in. Your edit will be placed in a queue until it is peer reviewed.

We welcome edits that make the post easier to understand and more valuable for readers. Because community members review edits, please try to make the post substantially better than how you found it, for example, by fixing grammar or adding additional resources and hyperlinks.

Required fields*

Rev

Title*

Body*

#Specific problem#
I am trying to communicate between a Python script and my Arduino Pro Mini using serial with a USB cable. In Python I can read what the Arduino writes but the Arduino can either not read what the Python writes or it is reading it in a form that I can't process. The most obvious way this manifests itself is when I try to write what the Arduino has just read from Python, to Python. Nothing gets displayed in Python.

My Arduino sketch appears to work just fine when I work with it in the Serial Monitor, i.e. it can read and write so I suspect it is something at the Python end. What's causing this?

#Details#
I want to be able test how quickly I can send 64 byte-long pieces of information to my Arduino. To do this I wrote a Python script that could should be able to periodically send various information to my Arduino. I can change the period and thus test what kind of speed I can get.

However, despite the fact that my Arduino sketch works just fine with Serial Monitor, i.e. I can send it information and read information from it, I can't get it to work with Python.

With my Python script I can open the connection and read what the Arduino writes, but for some reason there is a problem with writing from Python. I have tried the following but none of them have worked:

 - Using an Uno instead of a Pro Mini.
 - Putting a `Serial.println()` statement in my `get_data()` function. Nothing gets printed.
 - Sending a string with the format "T(number);" and using `sscanf()` to extract the number. Using an if statement to examine the number and turn an onboard LED on. Did not work.
 - Sending a string beginning with "T" and using an if statement to see if it is stored in `raw_data[]`. It isn't.
 - Writing the data from Python at different times (i.e. using a longer delay).
 - Writing from Python using `device.write(b"mystring")` and `device.write("mystring".encode())`

I'm at a loss for what to try next…

#Python (2.7) code#



 import serial, time, random, string

 device = serial.Serial('/dev/tty.usbserial-A105YOZX', baudrate = 38400)

 initial_time = time.time()
 current_time = time.time()

 counter = 0
 control = 0

 while counter < 1000:
 current_time = time.time()
 if current_time - initial_time > 0.1:
 initial_time = current_time
 counter += 1
 device.read()
 if current_time - initial_time > 1 and control == 0:
 device.write(b"Message being sent")
 control = 1

#Arduino code#



 #define RAW_LEN 64 //max length of incoming string (buffer size is only 64 bytes)
 
 //variables for incoming data
 char raw_data[RAW_LEN];
 int raw_data_i = 0; //index
 
 unsigned long my_time;
 int control = 0;
 int for_print;
 
 int get_data(int i) {
 //fills up raw_data[] with serial data. Clears raw_data if it gets too long
 if (Serial.available()>0) {
 raw_data[i] = Serial.read();
 Serial.println(raw_data[i]);
 //Serial.println(raw_data[i]);
 if (i<RAW_LEN-1){
 i++;
 }
 }
 return i;
 }
 
 void clear_data() {
 //clears raw_data and resets raw_data_i
 raw_data_i = 0;
 memset(raw_data,'0円',RAW_LEN-1);
 }
 
 //print functions
 void raw_print(char data[]) {
 Serial.println("Received data: ");
 //if (raw_data[0] == 'T') {digitalWrite(LED_BUILTIN, HIGH);}
 for (int i=0; i< RAW_LEN;i++) {
 Serial.println(data[i]);
 }
 }

 void setup() {
 Serial.begin(38400);
 Serial.println("Restart");
 pinMode(LED_BUILTIN, OUTPUT);
 digitalWrite(LED_BUILTIN, LOW);
 }
 
 void loop() {
 my_time = millis();
 raw_data_i = get_data(raw_data_i);
 //clear raw_data if it gets full
 if (raw_data_i == RAW_LEN-1) {
 clear_data();
 }

 if (my_time > 5000 && control == 0) {
 Serial.println("Here");
 raw_print(raw_data);
 control = 1;
 }
 }

Draft saved

Draft discarded

CollectivesTM on Stack Overflow