BlueNRG-M2SP module SPI not working as co-processor(replacing the BlueNRG-2N)

[malarab]

Hi everyone,

I designed a first custom PCB using the BlueNRG-2N as a coprocessor, and everything was working fine, I was able to control it with my main MCU over SPI without any issue.

Recently, I made a new version of the board where I replaced the BlueNRG-2N with the BlueNRG-M2SP module. I flashed it with the DTM firmware (BLUENRG-M2SP_DTM_SPI.hex) because I want to use it as a coprocessor.

I’m using exactly the same software as before for my main mcu (which should work), but now it doesn’t work at all : I don’t receive any data on the SPI MISO line from the BLE module.

I’ve attached both the old (working) and new designs. Since the firmware works with the BlueNRG-2N, I assume the issue is hardware-related. What could be wrong in my new design? Or what changes are required for the software ?

Also, I have a couple of additional questions:

1- There are multiple DTM firmware versions available (e.g. BlueNRG-M2SA_M2SP_DTM_Stack_v2.1c, v2.1e, and several others in the BlueNRG-1_2 DK 3.2.3)... Which one should I use for SPI coprocessor mode?

2- I was never able to connect to the BlueNRG-M2SP using the BlueNRG-1 ST-Link Utility, but it works fine with the RF Flasher Utility. Is this normal, or could it indicate a problem with my hardware?

Thank you,

Sincerely

[Laurent LOUAZON]

Hello,

Few comments here.
1) I agree an application FW running with BlueNRG-2N over SPI should be functional as well if using BlueNRG-M2 with same SPI interface.

However

2) BlueNRG-2N get the specific features to select UART or SPI interface through  DIO12.
This is not true with BlueNRG-M2. 
So handling DIO12 is useless with BlueNRG-M2. Customer should select UART or SPI interface and flash proper DTM FW version

3) You should flash a DTM SPI M2SP image with BlueNRG-M2SP (and logically DTM SPI M2SA image with BlueNRG-M2SA)
Internally, BlueNRG-M2SP is not having integrated SMPS and neither 32kHz Xtal.
So it is important to flash proper image (DTM_SPI_M2SP) from BlueNRG-1_2 DK 3.2.3\Firmware\BLE_Examples\DTM_M2SA_M2SP\BlueNRG-2

Regards
Laurent