nRF5340 GPIO Forwarder UART Default Pins Blocking SPI (P0.10/P0.11/P1.01)

[S M K Momin]

Dear Nordic Team,

I am working on a custom board using the nRF5340, and I have configured SPI with the following pins:

• SPIM_SCK → P0.08
• SPIM_MOSI → P0.09
• SPIM_MISO → P0.10
• SPIM_CS → P0.11
• Button → P1.01

However, I noticed that P0.10, P0.11, and P1.01 are by default assigned to /nrf-gpio-forwarder/uart functionality.

To disable this, I added the following in my board.overlay:

&gpio_fwd {
status = "disabled";
/delete-node/ uart;
};

I am also using BLE in my application.

Issue:
When I try to communicate with the SPI device:

• SCK and CS lines are toggling as expected
• MISO (P0.10) shows no activity
• The SPI device is not detected

Questions:

1. Can P0.10 be reliably used as SPI MISO on the nRF5340?
2. Is disabling gpio_fwd as shown above sufficient to free these pins and is miso will work with p010 every time?
3. Do I need to disable anything additional on the network core to permanently release these pins from UART/gpio-forwarder usage?

Any guidance on properly configuring these pins for SPI (especially in a dual-core + BLE setup) would be greatly appreciated.

Thank you!

[Kazi Afroza Sultana]

Hello,

Your approach is almost correct. To disable the gpio-forwarder functionality, you need to do only one method either disabling forwarder or deleting UART node. You have both now.

You can look at this case (+) nrf5340 Gpio forwarder availibility - Nordic Q&A - Nordic DevZone - Nordic DevZone.

Besides this setup in overlay, you can also set this CONFIG_SERIAL=n config in the network core config file (child_image/hci_ipc.conf).

[gopro]

As someone who recently worked with the nRF5340, I found that trying to both disable the GPIO forwarder and delete the UART node caused conflicts, so sticking to just one method worked reliably. Also, setting CONFIG_SERIAL=n in the network core config (child_image/hci_ipc.conf) ensured the serial interface didn’t interfere with HCI communication. This approach made the setup much cleaner and predictable.

FNF