Rpi Pico receiving on multiple UARTs

Question

Expected behavior:

in hardware I connect UART of a number 0/1 to the correct Pin numbers tx/rx and get it based on that connection

Actual behavior:

in hardware I connected UART of a number 0/1 to the correct Pin numbers tx/rx and got it on all of the related UARTs 0/1

I have this Array of UARTs where I can split them kinda like usb ports, and when I receive an input I get it from different indecies. to me it's a bit strange but it get's on all UART0 at once eventhough I'm connecting certain one only, or the same on all UART1.

ports = [
    UART(0, 115200, timeout=0, tx=Pin(0), rx=Pin(1)),
    UART(1, 115200, timeout=0, tx=Pin(4), rx=Pin(5)),
    UART(1, 115200, timeout=0, tx=Pin(8), rx=Pin(9)),
    UART(0, 115200, timeout=0, tx=Pin(12), rx=Pin(13)),
    UART(0, 115200, timeout=0, tx=Pin(16), rx=Pin(17))
]

The code:

from machine import UART, Pin
from time import time
import re

ports = [
    UART(0, 115200, timeout=0, tx=Pin(0), rx=Pin(1)),
    UART(1, 115200, timeout=0, tx=Pin(4), rx=Pin(5)),
    UART(1, 115200, timeout=0, tx=Pin(8), rx=Pin(9)),
    UART(0, 115200, timeout=0, tx=Pin(12), rx=Pin(13)),
    UART(0, 115200, timeout=0, tx=Pin(16), rx=Pin(17))
]

def read_ports():
    """Returns a list of ports with indecies that are receiving data"""
    port_list = []
    for i,port in enumerate(ports):
        if port.any() > 0:
            port_list.append({
                "port": port, "index": i
            })
    return port_list

request = [
    bytes(),
    bytes(),
    bytes(),
    bytes(),
    bytes()
]

while True:
    # Available Ports
    active_ports = read_ports()
    
    if len(active_ports) == 0:
        continue
    
    for uart in active_ports:
        index, port = uart["index"], uart["port"]
        byte = port.read(1)
        
        if byte == b'' or None or not byte:
            continue
        
        print("(index %d) (length %d) byte" % (index, len(request[index])), byte)

        request[index] += byte

If I have UART0 connected all UART0 get the bytes at random.

I just don't get it why? and how to solve it? and if it's normal behavior what is the point of having all of these UART ports if I can't use one when I need many?

Answer 1

There are only two UARTS on the Pico. They are identified as the channel 0 UART and the channel 1 UART.

For convenience each UART is routed to multiple GPIO.

See the table I give at https://abyz.me.uk/picod/py_picod.html#serial_open

  channel:= the channel to open (0 or 1).
   tx:= the GPIO to use for transmit.
        channel 0: one of 0, 12, 16, 28, 255.
        channel 1: one of 4, 8, 20, 24, 255.
   rx:= the GPIO to use for receive.
        channel 0: one of 1, 13, 17, 29, 255.
        channel 1: one of 5, 9, 21, 25, 255.
 baud:= baud rate in bits per second, 120 to 4000000.
  cts:= the GPIO to use for CTS.
        channel 0: one of 2, 14, 18, 255.
        channel 1: one of 6, 10, 22, 26, 255.
  rts:= the GPIO to use for RTS.
        channel 0: one of 3, 15, 19, 255.
        channel 1: one of 7, 11, 23, 27, 255.