STM32 SPI with CC1125 (TI)

[Andrew Neil]

The CC1125 is a TI sub-GHz transceiver: https://www.ti.com/product/CC1125

The User's Guide - https://www.ti.com/lit/pdf/swru295 - says that, after asserting CS, the SPI Master must wait for the CC1125 to pull MISO low before starting the transfer:

I think this means that the STM32F0's hardware SPI can't be used?

Unless anyone else can see a way ... ?

[Andrew Neil]

The CC1125 requires that CS remains asserted through the entire communication:

the CC1125 doesn't use the "TI protocol" described in the STM32F0 documentation:

(and that doesn't seem to cover waiting for MISO low anyhow)

 

[TDK]

Sounds like you would need to implement the CS pin and waiting logic itself, but could otherwise use it just fine.

• set CS low
• wait for MISO low
• call HAL_SPI_Transmit... or whatever
• set CS high

Waiting doesn't have to be a blocking operation although it would make the program logic a lot simpler.

The IDR register of the MISO pin is still connected/accurate in AF mode, so there's no issue reading it.

[Andrew Neil]

Yes, of course that works - why didn't I think of that in the first place!  <facepalm>

Now I have it working between an STM32F0-Disco and a CC1125 dev board.

But not working on the actual custom target board: the initial MISO sync works, but only zeros are ever read back. :frowning_face:

Anyone here with experience of STM32 + CC1125 can think of any gotchas! ?

(I've done it before with an AVR, and think I've got everything covered, but...)