WHO_AM_I issue in ASM330LHH

[Jigs]

I am using the ASM330LHH connected to the processor via 4-wire SPI communication. I’m trying to read the WHO_AM_I register, which should return 0x6B according to the datasheet, but I keep getting 0xFF. The CS line is set correctly before and after the transfer. What could be causing this incorrect data read? If the device isn’t found (WHO_AM_I doesn’t return 0x6B) and I still try to read accelerometer and gyro data, and I am getting data, will those values be completely random?

[Andrew Neil]

Welcome to the forum.

Please see How to write your question to maximize your chances to find a solution for best results.

In particular, please give full details of your setup - board(s) used, schematics, etc.

Some good, clear photos often help.

Also show your code - instructions in the above link.

---

@Jigs wrote:

but I keep getting 0xFF. 

---

0xFF is all ones, so possibly nothing at all is happening on the SPI - or, at least. on MISO.

---

@Jigs wrote:

The CS line is set correctly before and after the transfer. 

---

Have you verified that in the hardware?

Use an oscilloscope to verify that your SPI signals are good and clean and properly connected.

Use a logic analyser to see the SPI comms...

[TDK]

> What could be causing this incorrect data read?

Here are some possibilities:

• Bad code.
• Bad wiring.
• Not powered.
• Minsterpretation of data.

0xFF is a string of 1s and indicates the chip is not responding at all.

> If the device isn’t found (WHO_AM_I doesn’t return 0x6B) and I still try to read accelerometer and gyro data, and I am getting data, will those values be completely random?

You're never going to get random data. It'll probably also be 0xFF.