1.Multiple USB UART Bridge

This is multiple USB UART Bridge with Raspberry Pi Pico. I know there are some similar implementations, but this has useful additional functions for dev environment.

6 USB-UART Bridges
- 2 Pico Hardware UARTs
- 4 PIO Based UARTs provided by Arduino Pico/RP2040 board package
Pico USB Console other than the Bridges is also available for some functions
- Capturing USB-UART Bridged data
- counts Tx/Rx Bytes of each USB-UART Bridge

Before

After

2.How To Use

2.1.Write UF2 to Pico and connect to your PC

You can use complied UF2 file in convenient.
If you will build UF2 yourself see #4.Build Requirement

2.2.Find COM port numbers if you use windows

This is troublesome work but needed. You can find 7 new USB COM ports on Device Manager.

Find COM ports witch 'Device Instance Path' of property is
USB¥VID_2E8A&PID_000A&MI_00¥...
Note the linked COM port numbers
USB¥VID_2E8A&PID_000A&MI_00¥...
MI_00 = Pico USB console
MI_02 = USB-UART Bridge 0
MI_04 = USB-UART Bridge 1
MI_06 = USB-UART Bridge 2
MI_08 = USB-UART Bridge 3
MI_0a = USB-UART Bridge 4
MI_0c = USB-UART Bridge 5

I changed COM port FriendlyName in the Registry at my own risk to escape from pain.

2.3.Connect devices to Bridge UARTs

Bridge	GPIO Pin (Tx/Rx)
USB-UART Bridge 0	0/1
USB-UART Bridge 1	4/5
USB-UART Bridge 2	8/9
USB-UART Bridge 3	12/13
USB-UART Bridge 4	16/17
USB-UART Bridge 5	20/21

3.Example

The environment

graph LR;
    1(PC)<-.->|COM9/Bridge0 USB|2(USB-UART-Bridge/Pico);
    1<-.->|COM7/Pico console|2;
    2<-.->|Bridge0 UART|3(DeviceA);

3.1.'help' at USB console

Type 'help' at COM7 terminal. This is vscode SERIAL MONITOR example.

---- Sent message: "help\n" ----
Usage: 
  show              : show current parameters
  cap num           : enable capture for bridge<n>
  uncap num         : disable capture for bridge<num>
  capmode num mode  : set capture mode for bridge<num> to <mode>
                    : mode: 1=TXT, 2=HEX, 3=TXT&HEX
  clear {num | all} : clear bytes count
  help              : print this help

3.2.setup to capture data stream

Type 'cap 0', 'capmode 0 1' and 'show'

---- Sent message: "cap 0\n" ----
Capture:
  enable for B0 (GP0/1)
---- Sent message: "capmode 0 1\n" ----
Cpature mode:
  B0 (GP0/1) capture mode to 1
---- Sent message: "show\n" ----
Show:
  bridge        |  baudrt | capture | capmode | capdelim  |  usb->uart |  uart->usb
  B0 (GP0/1)    |  115200 | off     | TXT     | \n  ( 10) |        474 |      85463
  B1 (GP4/5)    |  115200 | off     |     HEX | \n  ( 10) |          0 |       8261
  B2 (GP8/9)    |  115200 | off     |     HEX | \n  ( 10) |          0 |          0
  B3 (GP12/13)  |  115200 | off     |     HEX | \n  ( 10) |          0 |          0
  B4 (GP16/17)  |  115200 | off     |     HEX | \n  ( 10) |          0 |          0
  B5 (GP20/21)  |  115200 | off     |     HEX | \n  ( 10) |          0 |          0

3.3.capture 'Hello World !'

Run sample MicroPython Program at the DeviceA

import time
from machine import UART,Pin

u = UART(0, 115200)
i = 0
while True:
    u.write(str(i))
    i += 1
    u.write(' Hello World !\n')

    time.sleep(1)

Then the Bridge captures them at COM7

B0 (GP0/1) (uart->usb txt):0 Hello World !\n
B0 (GP0/1) (uart->usb txt):1 Hello World !\n
B0 (GP0/1) (uart->usb txt):2 Hello World !\n
...

COM9 terminal shows

0 hello World !
1 hello World !
2 hello World !
...

4.Build Requirement

Required software
- Arduino IDE
- Arduino Pico/RP2040 board package
- current UF2 is built with Arduino IDE 1.8.19 and RP2040 package 2.5.2
Board Configuration
- Use Adafruit TinyUSB as USB stack in the board configuration menu
You have to change some package source code
- '#define CFG_TUD_CDC 1' to '#define CFG_TUD_CDC 7'
  in the tusb_config_rt2040.h
- 'uint8_t _desc_cfg_buffer[256];' to 'uint8_t _desc_cfg_buffer[1024];'
  in the class Adafruit_USBD_Device in the Adafruit_USBD_Device.h

5.Important Notes

UART Baudrate is fixed 115200 bps. if you change it you have to change source code.
Use LF or CRLF to send commands to Pico USB console.
Capture function is for light debugging purpose. Capturing multiple bridges at the same time can overflows the buffer.

6.Command Details

6.1.cap / uncap

Enable / Disable capture on each bridge.
bi-directional data streams are captured simultaneously.

6.2.capmode

Captured data is displayed in TEXT, HEX or TEXT&HEX.
If you choose TEXT mode and data stream contains bytes which numbers is greater than 127, the text could be unreadable. Control characters less than 128 are translated readable strings.
In HEX mode, the data column is divided into 16 byte units and displayed. data less than 16 bytes will be displayed 1 second after being received.
In TEXT mode and TEXT&HEX mode, the data is divided by delimiter. If a text column exceeds buffer size, the text column is divided into buffer size units.

6.3.capdelim

You can specify the delimiter which is a character byte.
There are three ways to specify.
1. A number from 0 to 255.
2. A special character \0 \b \t \n \v \f or \r.
3. A character such as /.
If you wanna specify SPACE character, use number 32.

7.ToDo

triggered capturing
rewriting data stream
UART-UART Bridging and capturing by USB
and so on..

zbn10/USB-UART-Bridge