Get default Pins for Serial, SPI, I2C

[jumjum123]

I'm using Espruino on several boards.
Questions often coming up are like "which pins are TX/RX on Serial1"
My idea was to add a function to Serial Class for that "Serial1.getPins" that returns an object with tx, rx, ...
Got this running (tested on ESP32 only, yet).
Next step was to code something similiar for SPI and I2C, and failed. Found a way to getPins after calling setup only.
Any idea ?

[gfwilliams]

That sounds like a good plan. On STM32 we have some functionality already that provides help if you use a pin that's not supported (in fact it's in the main Espruino codebase).

• This: https://github.com/espruino/Espruino/blob/master/src/jspin.c#L416
• Called from https://github.com/espruino/Espruino/blob/master/targets/stm32/jshardware.c#L2197

So you could just put a line in for ESP32 to do that? Although my understanding was on ESP32 you can generally use any hardware peripheral on any pin, it's just that some pins were marginally faster that others for very high speed stuff?

It's not been an issue on nRF52 because any peripheral can go anywhere.

We do also have documentation auto-generated for all the boards, eg https://www.espruino.com/ESP32#gpio-pins

[jumjum123]

Hmm, will take a closer look into these.
I'm more or less searching more convenience in coding for use on several boards.
Example:
There is a mp3 player, controlled by serial port.
Easy solution is to use Serial2 with default pins.
Using this code on a different board needs to wire the pins to the new board, nothing else.
But for that I need to know, which pins are behind tx and rx.
Right now (AFAIK) I have to search in sources for the pins.

One solution would be to ask the board for the pins. Thats what I tried first.
OK, I also could create a table for all boards and add it to documentation.
But for me its much more fun to code a solution ;-)

[gfwilliams]

Actually one more thing I remembered which does exist, is pin.getInfo().functions

So I believe right now you could iterate over all the pins in the board, something like:

for (var i=0;Pin(i);i++) print(Pin(i).getInfo().functions)

And check that the function provided matches what you want - I think that works on everything. It actually makes a little more sense than Serial1.getPins() because on devices like STM32, Serial1 can usually be in two distinct places - so getPins would have to return an array anyway

[jumjum123]

It was a kind of surprise to check your suggestion on an ESP32 board. There are only a few lines. After digging through some scripts and sources, the reason is in boards/ESP32.py I've added some lines, see attached file. Would be great if you could check my changes in attached file. @mark, please take a closer look also Am Di., 11. März 2025 um 14:09 Uhr schrieb Gordon Williams < ***@***.***>:

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Actually one more thing I remembered which does exist, is pin.getInfo().functions So I believe right now you could iterate over all the pins in the board, something like: for (var i=0;Pin(i);i++) print(Pin(i).getInfo().functions) And check that the function provided matches what you want - I think that works on everything. It actually makes a little more sense than Serial1.getPins() because on devices like STM32, Serial1 can usually be in *two* distinct places - so getPins would have to return an array anyway — Reply to this email directly, view it on GitHub <#7702 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAPYNHQSGJRF2EURZCF7WNT2T3N77AVCNFSM6AAAAABYYKVPROVHI2DSMVQWIX3LMV43URDJONRXK43TNFXW4Q3PNVWWK3TUHMYTENBWGE3TGMA> . You are receiving this because you authored the thread.Message ID: ***@***.***>

[jumjum123]

Sorry, github doesn't like my uploaded file (?)
You can get it here https://www.jumware.com/Temp/ESP32.py
Changes are starting at line 187

[gfwilliams]

I'm not sure I understand why you changed UART1 to UART0 and re-ordered everything? I'm wondering whether actually you we using an out of date version of Espruino which didn't have those changes in?

See the current one: https://github.com/espruino/Espruino/blob/master/boards/ESP32.py

The current version already seems to contain most of this stuff and the UART0->1 change was because UART0 isn't valid - it was added 2 months ago and maybe your fork doesn't have the code?

[jumjum123]

Sorry, my fault, I was still working with V2_24. Thanks for guiding me back to the road.

There is only one question left in ESP32.py, SERIAL2 or USART2 is missing.
According to jshardwareUart.c line 67-69 tx is pin 4 and rx is pin 5 for SERIAL2
If there is somehing wrong in my understanding, please correct me ;-)

[gfwilliams]

Actually looking at jshardwareUART we should probably use the auto pin selection code that @SimonGAndrews added for I2C and SPI there so it works on other boards.

I looked into UART2 and it seems it was probably left out because the default pins for it are on 9/10 but those can't be used because they're used for the SPI flash - so you have to use other pins - and as I said ESP32 can use any pins you want to for serial by the look of it. Info at https://randomnerdtutorials.com/esp32-uart-communication-serial-arduino

But I've just added pins in for 4/5 as you say as at least it'll show what the current defaults are