thingy91x nrf5340 bmi270 spi no communication

RE: thingy91x nrf5340 bmi270 spi no communication

Benjamin — Mon, 17 Nov 2025 19:18:27 GMT

Hi,

The default configuration gives the I2C and SPI to the nRF9151. These buses can only be controlled by a single host.

The thingy91x_no_buses.dtsi file shows how you can disable the buses on the nRF9151. You will also need to use a different partition layout since the secondary app partition is on the SPI flash by default. This is already done with this file. One way to apply that memory layout is by adding the following Kconfig symbol in sysbuild.conf:

SB_CONFIG_THINGY91X_STATIC_PARTITIONS_NRF53_EXTERNAL_FLASH=y

There is also a bug in NCS 3.1.1 where this symbol can only be selected on the nRF53 side. The quick fix is to remove this line. See this PR.

Best regards,
Benjamin

RE: thingy91x nrf5340 bmi270 spi no communication

SergeiA — Thu, 13 Nov 2025 04:09:35 GMT

I got similar problem on Thingy:53. With very similar settings and same internal BMI270. What I see is bmi270 fails to initialize way before my code tries to use it, it is back in driver initialization. When driver attempts to init this sensor it reads deviceId, and in my case it is always 0, not what driver code expects. After that game is over, any call to device_is_ready() just checks flag that was set during driver initialization and return false. I traced system calls before driver reads deviceId at the first time, and it seems that all SPI settings like mode, CS level, clock polarity, etc - are compatible with bmi270 specs. I had issues with other sensors because of that, but not in this case.

I tried to find any Nordic sample that uses bmi270, nothing there. Edge Impulse firmware uses second internal accelerometer, not bmi270, it works for them, but I need gyro data.

So my request is: nice people in Nordic Semi, could you provide a simple working sample, that successfully reads data from bmi270?

It could be useful for us to see, how to enable this sensor in overlay, what kind of config settings to use. I understand that bmi270 is really funky beast -- it requires loading 6kb of code into the chip, it could do this and that -- but I have it failed on the very first access, before all this. If it is broken, I could appreciate that you will tell it and we will stop wasting time on fixing it.

Thank you,

Sergei

RE: thingy91x nrf5340 bmi270 spi no communication

MartinPDU — Tue, 11 Nov 2025 14:18:03 GMT

The VDD_BMI270 @SB4 is 1.734V when running the code.

RE: thingy91x nrf5340 bmi270 spi no communication

MartinPDU — Tue, 11 Nov 2025 10:22:15 GMT

What about the load switch for the bmi supply? How is it activated?

RE: thingy91x nrf5340 bmi270 spi no communication

MartinPDU — Tue, 11 Nov 2025 08:55:04 GMT

Hi Benjamin,

yes, we are talking about the onboard BMI270.

We can read out the BMI270 from the nrf9151 side. However, if we flash a blinky sample on the 9151 and try to read out the BMI270 via the nrf5340, it is not accessible as described.

Is there possibly a problem with the 5340 device tree?

Best regards,
Martin

RE: thingy91x nrf5340 bmi270 spi no communication

Benjamin — Tue, 11 Nov 2025 08:17:58 GMT

Hi Martin,
Thanks for writing us, I assume you are talking about the onboard BMI270 or an external one?

Best regards,
Benjamin