Sending data over Serial

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Sending data over Serial#

When a Pico is connected to a computer using a USB cable it is possible to send data over the serial connection

Requirements

  1. A Pico

  2. A Computer connected to the Pico by USB

Set-up#

Connect the Pico and Computer together using a USB cable.

The following program is run on the Computer, Not The Pico

"""Simple program to log data sent over the serial port"""

import sys

import datetime as dt
import json
import serial


def readserial(comport: str, baudrate: int):
    """Function to read value from a serial port
    Assumes it is a json formatted string

    Parameters
    ----------
    comport : str
        the com port to connect to
    baudrate : int
        the baud rate of the connection
    """
    ser = serial.Serial(
        comport, baudrate, timeout=0.1
    )  # 1/timeout is the frequency at which the port is read

    try:
        while True:

            data = ser.readline().decode().strip()

            if "{" in data:
                #This assumes the data is JSON formated
                data = json.loads(data)
                print(data)
                # This can be saved to file or database depending on need
            elif data:
                #This just prints it, but it could be an error from the pico and therefore treated accordingly
                print(data)
    except KeyboardInterrupt:
        print("Ending Logging")
        sys.exit()


port = # The COM port that is connect
baud = 115200 # The baud rate of the connection, normally 115200

readserial(port, baud)

The code on the Pico is then below. Note that this code can recieve commands on the serial port

import os
import sys
import microcontroller
import time
import json
import board

import supervisor



def hola(input_buffer:str):
    print(f"Hello from {inatorname}")
    
def reading():
    try:
        temp = 50   #Fixed as an example
        humidity = 45 # fixed as an example
        #Create dictionary
        json_dict = {"inator":inatorname,"temperature":temp,"humidity":humidity}  # Send data with JSON syntax
        json_data = json.dumps(json_dict)
        #print(f"{json_data}")
        return json_data
    except RuntimeError as e:
        print(f"Sensor read error: {e}")
        return None
#Retrieve variables from settings.toml
inatorname = os.getenv("INATORNAME")
accTime = float(os.getenv('ACQUIRETIME'))  #how often to acquire and transmit data

last_publish = 0
input_buffer = ""

while True:
    
    now = time.monotonic()
    if supervisor.runtime.serial_bytes_available:
        char = sys.stdin.read(1)
        if char in ("\n", "\r"):
            if input_buffer:
                print(f"Received command: {input_buffer}")
                if input_buffer == "hola":
                    hola(input_buffer)

                if input_buffer == "read":
                    json_data = reading()
                    if json_data:
                        print(f"{json_data}")
                        
                input_buffer = ""
        else:
            input_buffer += char
            
            
    if now - last_publish >= accTime:
        json_data = reading()
        if json_data:
            print(f"{json_data}")

        last_publish = now

    time.sleep(0.01)

in the settings.toml file on the Pico put the following:

INATORNAME = "NAME"
ACQUIRETIME = 5
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