Why is my UART communication between X-NUCLEO-BNRG2A1 (BlueNRG-M2SP) and Nucleo-G070RB not working?

Question

I am currently having trouble making a simple UART communication (+ the HCI command-based protocol) between the X-NUCLEO-BNRG2A1 shield embedding a BlueNRG-M2 (which itself embeds a BlueNRG-2) and my Nucleo-G070RB. I cannot use SPI for this.

I also created a ST topic

First, on X-NUCLEO-BNRG2A1 side (BlueNRG-2) :

• I downloaded the FW package STSW-BNRG2N-V320
• I used the documentation UM2666 "Getting started with the X-CUBE-BLE2 Bluetooth Low Energy software expansion for STM32Cube" as support,
• I flashed the X-NUCLEO-BNRG2A1, i-e the embedded BlueNRG-2, using the BlueNRG-1_2 Flasher Utility (STSW-BNRGFLASHER), with the STSW-BNRG2N-V320 in order to emulate it with a BlueNRG-2N -I removed all Resistors / Jumpers from the SPI and unnecessary lines : (SPI_MOSI R80 & SPI_MISO R79 ), (SPI_CSN R77), (SPI_IRQ / BOOT R85 & R82) , (SPI_CS R70, R76 & R86), (GPIO R81 & R84), (Jumpers J11, J12, J13, J14, J15 (I have a doubt about J15, but I think this is just required while flashing) )
• I added all required 0 Ohm Resistors + Jumpers : R83 for DIO12 (SEL pin on BlueNRG-2N) & Jumper J10 (3v3 <-> VDD).
• I also added 0 Ohm Resistors R71 and R73 as I firstly thought these 2 lines (DIO4 & 5) were the UART lines. But if I understood correctly, these are just for application serial com when used and the emulation of BlueNRG-2N uses the DIO8 & DIO11 as UART Pins.

Then, on NUCLEO-G070RB side (STM32G0xx) :

• I have an already working project running correctly on this board
• I took the following project example: STM32L - BLE_Beacon_NWK from BlueNRG-1_2 DK 3.2.3 and extracted all I needed , using the documentation "STM32L - BlueNRG-1,2 network coprocessor (UART mode)" from the doxygen doc as support.
• I made an UART Rx/Tx module working, using the HCI commands defined in the imported libraries. This module is correctly working in:
  • TX because I validated it using a USB to Serial converter on my laptop with a python script using a hci lib : the data is correctly sent.
  • RX because if I make the loop TX <-> RX on the same UART, I receive exactly what was sent. I haven't tested the reception of HCI Events data, but that is not the pb here.

Finally, I mapped / configured / checked the GPIOs / buses like this:

• BlueNRG-M2SP Pins 1 & 2 untouched
• BlueNRG-M2SP Pin 3 = DIO4 = ? < --- > STM32G0xx PA9 = unused & floating
• BlueNRG-M2SP Pin 4 = DIO5 = ? < --- > STM32G0xx PA10 = unused & floating
• BlueNRG-M2SP Pin 5 = VDD is correclty at 3V3
• BlueNRG-M2SP Pins 6 & 7 untouched
• BlueNRG-M2SP Pins 8 correctly grounded
• BlueNRG-M2SP Pins 9 untouched
• EDIT " BlueNRG-M2SP Pin 11 = DIO11 = UART_RXD (BNRG-2N) " < --- > STM32G0xx PB2 = USART3_TX.
  • When unconnected and BlueNRG-M2SP in correct state, pin is correclty floating
  • When connected + a USB Serial converted RX wire connected, HCI data is good (interpreted by py python)
• EDIT " BlueNRG-M2SP Pin 10 = DIO8 = UART_TXD (BNRG-2N) " < --- > STM32G0xx PB0 = USART3_RX
  • When unconnected and BlueNRG-M2SP in correct state, pin is correclty at 3V3, and drops to floating when BlueNRG-M2SP is in reset
  • When connected to RX wire of a USB Serial converter or a Scope NOTHING, stays at 3v3
• BlueNRG-M2SP Pins 12 to 18 untouched
• BlueNRG-M2SP Pin 19 = RESETN < --- > STM32G0xx PA8 = GPO set to 1 when want to enable the BRNG. Correctly set to 1 during communication
• BlueNRG-M2SP Pin 19 = DIO12 = SEL (BNRG-2N) < --- > STM32G0xx PB4 = GPO set to 1 when want to enable the UART. Correctly set to 1 during communication

As a result, BlueNRG-M2SP should be working as BlueNRG-2N: is powered up & grounded correclty, is enabled (resetn = 1) & SEL pin = 1 for UART, has UART TX & RX mapped & receives good HCI commands, but no response and my application commands end all in timeout.

I tried swapping RX & TX just in case, nothing either.

Have I missed something ? Like the DIO 4 & 5 are maybe the ones to use ? The "emulation" FW is not UART HCI protocol compatible ?

I really appreciate any response, I am a bit in a pickle here ... ‌‌

Max.Pach

Answer 1

Copied reply from ST community:

Nevermind, seems to come from the way you flash the BlueNRG board ...

I was using the X-NUCLEO-BNRG2A1 & the STEVAL-IDB008V2. Using the latter, I of course made the HW workarounds to enable external com without having the embedded components in the way.

Using RF Flasher and a bunch of different Example apps (DTM Uart, Beacon, the BlueNRG 2N "emulation"), no response, on both boards.

• SWD only for X-NUCLEO-BNRG2A1
• SWD & UART with STEVAL-IDB008V2 (as there is a USB to serial converter STM32 on the board that manages that flashing function). No response with GUI either.

Using the BlueNRG DK graphical app, I managed to flash through UART the STEVAL-IDB008V2 with a DTM Uart image that now communicates with Both GUI & my FW on external Nucleo-G070RB. Howerver, when I compare the flash with the DTM Uart image using RF Flasher, there are differences.

I am really confused with that. This should not happen. Flashing the device with an example bin from the BlueNRG DK folders through RF Flasher should work. Now I am stuck with the X-NUCLEO-BNRG2A1 not working as there is no way to program it using the BlueNRG DK graphical app.

So what I am missing there ? I will try on Ubuntu using OpenOCD but I fear the same result will happen.