[bug] Wrong Pins assigned to Serial1

[Prasana-sys]

Hardware

xG24 Explorer Kit

Core version

2.3.0

Arduino IDE version

2.3.5

Operating system

Windows 11

Radio stack variant

BLE

OpenThread Border Router device (if using Matter)

No response

Issue description

In pins_arduino.h for the xG24 Explorer Kit, Serial1 pins are defined as:

#define PIN_SERIAL_RX1 (A7) // PA0
#define PIN_SERIAL_TX1 (A6) // PB1

https://github.com/SiliconLabs/arduino/blame/c51e6c01f2e90f46d08e6d530a015531050cc42c/variants/xg24explorerkit/pins_arduino.h#L85

I believe this is wrong and it should be RX1 -> A5 (PD5) and TX1 -> A4 (PD4) as listed on the datasheet and from what I can see physically on the board. Please reconfirm this.

Serial output

No response

RTT output (if using Matter)

No response

Minimal reproducer code

No response

[silabs-bozont]

Hello @Prasana-sys,
Thank you for your bug report! According to the original manual and the MikroBUS header pinout you're right - the Serial1 pins should be at PD4 and PD5.
However to fit all the peripherals we had to make some puzzle moves. We added an additional SPI (SPI1) which is shared with Serial1 using the EUSART0 peripheral - which doesn't allow mapping to PortC and PortD pins.
Right now the xG24 Explorer Kit's EUSART/USART peripheral mapping looks like this:

• USART0 -> Serial (USB)
• EUSART0 -> Serial1 or SPI1
• EUSART1 -> SPI

I'll look into whether it's possible to shuffle the peripherals around to get the correct mapping for Serial1 in order to not break the MikroBUS pinout. This'd also mean that the SPI1 has to move with Serial1 as well.

Here's the current Arduino pinout for reference:

[silabs-bozont]

Hello @Prasana-sys,
I've remapped the USART/EUSART peripherals on the xG24 Explorer Kit to match the mikroBUS pinout. It was possible to swap around the USART/EUSART peripherals to have the correct layout.
The new USART/EUSART mapping for the xG24 ExpKit is:

• USART0 -> SPI
• EUSART0 -> Serial (USB)
• EUSART1 -> Serial1, SPI1

Here's the updated pinout:

Changing this opened a bigger rabbit hole than I expected - a few adjustments were also needed in the SPI driver - but thankfully everything works as expected with the new layout as well.

I also changed the pin mapping on the Ezurio Lyra 24P - which was having a similar mapping issue.
The changes will be included in the next release!