Problem with board pin assignments on Challenger RP2040 LTE

[psturgeon54]

CircuitPython version

Version:  adafruit-circuitpython-challenger_rp2040_lte-en_GB-8.2.2.uf2

Code/REPL

import board
dir(board)

Behavior

Adafruit CircuitPython 8.2.2 on 2023-08-01; Challenger RP2040 LTE with rp2040

import board dir(board) ['class', 'name', 'A0', 'A1', 'A2', 'A3', 'A4', 'A5', 'D0', 'D1', 'D10', 'D11', 'D12', 'D13', 'D5', 'D6', 'D9', 'GP0', 'GP1', 'GP10', 'GP11', 'GP12', 'GP15', 'GP16', 'GP17', 'GP19', 'GP2', 'GP21', 'GP22', 'GP23', 'GP24', 'GP25', 'GP26', 'GP27', 'GP28', 'GP29', 'GP3', 'GP4', 'GP5', 'GP6', 'GP7', 'GP8', 'GP9', 'I2C', 'LED', 'MISO', 'MOSI', 'RX', 'SARA_BTN', 'SARA_CTS', 'SARA_PWR', 'SARA_RST', 'SARA_RTS', 'SARA_RX', 'SARA_TX', 'SCK', 'SCL', 'SDA', 'SPI', 'TX', 'UART', 'board_id']

Description

I am trying to use the Challenger RP2040 LTE pin labelled SDI on the PCB, but I am having trouble.

According to the Challemger RP2040 LTE circuit, this connection goes to the RP2040 chip on its pin 31 which is GPIO20. Using the board module in the latest release of CircuitPython for this board, I have created a simple test program which assigns all the external board pins as inputs with pull-up. The test program then displays on REPL the pin ID of any pin which is grounded. This works for every pin on the board, except the pin labelled SDI (i.e. the pin between the ones labelled SDO and RX)

I have a hunch that the board module content for this particular pin may be incorrect, possibly because board does not have an SDI or GP20 attribute

Additional information

No response

[anecdata]

On this pin diagram, SDI is IO24 / GP24. IO20/ GP20 and IO18 / GP18 aren't exposed. Are you looking at something different? https://ilabs.se/challenger-rp2040-lte-datasheet/ Here's the mapping of raw pins to board names:

microcontroller.pin.GPIO0    board.GP0 board.SDA 
microcontroller.pin.GPIO1    board.GP1 board.SCL 
microcontroller.pin.GPIO10   board.D11 board.GP10 
microcontroller.pin.GPIO11   board.D10 board.GP11 
microcontroller.pin.GPIO12   board.D9 board.GP12 
microcontroller.pin.GPIO13   board.SARA_BTN 
microcontroller.pin.GPIO14   board.SARA_RST 
microcontroller.pin.GPIO15   board.GP15 board.SARA_PWR 
microcontroller.pin.GPIO16   board.D0 board.GP16 board.TX 
microcontroller.pin.GPIO17   board.D1 board.GP17 board.RX 
microcontroller.pin.GPIO18   
microcontroller.pin.GPIO19   board.GP19 board.LED 
microcontroller.pin.GPIO2    board.D5 board.GP2 
microcontroller.pin.GPIO20   
microcontroller.pin.GPIO21   board.A5 board.GP21 
microcontroller.pin.GPIO22   board.GP22 board.SCK 
microcontroller.pin.GPIO23   board.GP23 board.MOSI 
microcontroller.pin.GPIO24   board.GP24 board.MISO 
microcontroller.pin.GPIO25   board.A4 board.GP25 
microcontroller.pin.GPIO26   board.A3 board.GP26 
microcontroller.pin.GPIO27   board.A2 board.GP27 
microcontroller.pin.GPIO28   board.A1 board.GP28 
microcontroller.pin.GPIO29   board.A0 board.GP29 
microcontroller.pin.GPIO3    board.D6 board.GP3 
microcontroller.pin.GPIO4    board.GP4 board.SARA_TX 
microcontroller.pin.GPIO5    board.GP5 board.SARA_RX 
microcontroller.pin.GPIO6    board.GP6 board.SARA_CTS 
microcontroller.pin.GPIO7    board.GP7 board.SARA_RTS 
microcontroller.pin.GPIO8    board.D13 board.GP8 
microcontroller.pin.GPIO9    board.D12 board.GP9 

[psturgeon54]

Here is the circuit from iLabs for the Challenger RP2040 LTE: https://gitlab.com/invectorlabs/hw/challenger-rp2040-lte/-/blob/main/V0.2/challenger-rp2040-lte.pdf?ref_type=heads

On the circuit, the connection labelled SDI on header JP2 goes to the RP2040 pin shown as GPIO20. I see that this pin has no assignment in the microcontroller.pin mapping table. microcontroller.pin.GPIO20 has no assignment

[psturgeon54]

I suspect there may be other errors in the pinout diagram shown in https://ilabs.se/challenger-rp2040-lte-datasheet/ I tried raising this matter with Pontus Oldberg of ILabs, but he hasn't yet replied to an email I sent him with a detailed explanation of why I think the labelling of one of the other pins is wrong. I haven't had time to check through the details of every single pin, but I suppose that various issues will be apparent if you consult the circuit diagram for all the pins on JP1 and JP2 and refer to the RP2040 datasheet section 1.4 of https://datasheets.raspberrypi.com/rp2040/rp2040-datasheet.pdf

I can well understand how errors might creep in where there is such a profusion of pin names, pin IDs and different functions that the RP2040 can map to each of its GPIO pins

[anecdata]

Ah, I see. I hadn't found the schematic. On the schematic, pins 18 and 24 are unconnected.

You can use microcontroller.pin.GPIO20 in CircuitPython in code in place of board.*, to confirm that the schematic is correct and the pin diagram is wrong.

[tannewt]

FYI @PontusO

[anecdata]

The schematic is indeed wrong.

>>> led = digitalio.DigitalInOut(microcontroller.pin.GPIO20)
>>> led.direction = digitalio.Direction.OUTPUT
>>> 
>>> led.value = True
>>> led.value = False
>>> 
>>> led = digitalio.DigitalInOut(microcontroller.pin.GPIO24)
>>> led.direction = digitalio.Direction.OUTPUT
>>> 
>>> led.value = True
>>> led.value = False

The second set of code, using pin 24 (in code: microcontroller.pin.GPIO24, board.GP24, or board.MISO), toggles an external LED connected to the pin marked on the silk as SDI. Using pin 20 does nothing.

[psturgeon54]

Thanks for the tips. I had assumed that the circuit schematic was the gold-standard for what was actually connected to what. Since the schematic showed the JP2 SDI pin connected to RP2040 GPIO20 and GP20 was not in the list of board. assignments you gave, I figured that was why my simple test program couldn't get that pin to work as an input using board.. I will have a crack at what you suggest tomorrow. Clearly something is amiss in either the schematic, the Challenger LTE pinout diagram or the board module. We shall see...

[psturgeon54]

Having updated my test program as you suggested, I can now confirm that the pin labelled SDI on the Challenger RP2040 LTE is indeed microcontroller.pin.GPIO20. I suppose this proves that the schematic is correct and that the pinout diagram has at least one error. According to the schematic RP2040 GPIO24 is unconnected. I presume then that the mapping should be something like

microcontroller.pin.GPIO20 board.SDI board.GP20

[anecdata]

Do you have a Mk I or a Mk II board? I have a Mk I (original, not labeled Mk I).

I've asked about this also on the iLabs Discord.

[psturgeon54]

We purchased ours form Pi Hut in January this year. I can see from the order confirmation email that the order was for the MK II version.

However, I have looked very closely at the PCB under our workshop pcb microscope, and I can't see anything on the PCB silk-screen which specifically indentifies it as being a Mk II.

[anecdata]

That could account for it, we probably need iLabs to clarify. Assuming the versions are different, that will complicate what to do about the board definition.

But for now, any code can use microcontroller.pin.GPIO* instead of board.GP* or another alias.

[anecdata]

Reply on iLabs Discord indicates there was a change between board revisions https://discord.com/channels/731576543050203147/902533648874618880/1139222674229432370

[jepler]

That link doesn't appear to work if you're not already a member of the discord. If there's any additional useful content in the message can you add it here by copypaste?

[anecdata]

iLabs Electronics — Today at 10:44 AM I saw I was tagged on github for this issue. I'm on vacation right now but will look into it on monday. But as a quick response to this, yes we did make a revision to the board with regards to io24 and io20. The first version was incorrect making it difficult to use SPI (io24 can't be used as SDI).

[psturgeon54]

I'm still very much of a beginner with CircuitPython, so your handy tip about how to use microcontroller.pin.GPIOx instead of board.* was a big help.

Since you are clearly some rungs higher up than me on the Challenger LTE, CircuitPython and github ladders, I am wondering whether you might like to discuss a project I'm working on that uses Challenger LTE to run a Blynk client. I presume that this isn't the place to have such a discussion. If you are interested, my email is psturgeon@agiltechnik.cloud.

[anecdata]

Adafruit Discord is a great place to discuss projects like that: https://adafru.it/discord It's a community of mostly hobbyists and volunteers, very helpful on a variety of topics.

[psturgeon54]

Thanks again. I imagine there are quite a few hobbyists who know an awful lot more than me about the relevant issues. I'll be along to discord in a wee while.