How to wire BlueNRG-M2SA for UART communication

[SPhil.3]

What pins should we use if we would like to interface with the BlueNRG-M2SA module via UART. We currently use a UART interface on an older competing Bluetooth module and would like stay with that communication interface instead of SPI which is used on the evaluation boards.

My schematic is currently wiring up a STM32L475RC processor to the BlueNRG-M2SA module as follows.

USART3_TX --> Pin 3 DIO4

USART3_RX <-- Pin 4 DIO5

USART3_RTS --> Pin 15 DIO0

USART3_CTS <-- Pin 9 DIO6

I have our RTS signal connected to DIO0 instead of DI07 because we plan to actively drive DIO7 as part of the BOOT feature. I would like to use whatever the default UART pins are so as to minimize software work.

I also have a question about the GND on pin 21. On the schematic for the STEVAL-IBD008V1M evaluation board, this pin is called GND_RF. There is also an inductor L3 in series between the pin and GND. Is this needed and if so, what is the value or manufacturer part number? This is not described in the datasheet.

I have attached a snippet of our preliminary schematic. I also attached a snippet of the the STEVAL-IBD008V1M schematic which shows L3.

Thank you for your assistance.

[Laurent LOUAZON]

Hello,

Could you clarify which FW you are planning to use inside BlueNRG-M2SA?

Is it a DTM UART so that you will use it as network processor?

Will it have sleep mode?

If HW flow control mandatory ? What is UART speed targeted here?

I recommend having a look at BlueNRG-2 that is the SoC used inside BlueNRG-M2SA.

It will provide more details and resources.

About your point:

• I would not recommend using DIO4/5 for UART Tx/Rx if you are willing to do FW upgrade through UART (and handle DIO7 boot pin). Only DIO7/11 are addressing UART bootloader.
• Now DIO7/DIO11 UART pins are not having HW flow control. You should implement this FW flow control through SW if willing to use this UART.
• Note that only DIO9/10/11/12/13 are wake up capable with BlueNRG-2 but DIO13 is not output on BlueNRG-M2SA. This is is related to my comments if using a FW with sleep mode so that a pin having wake up capability should be used for RTS.But I see you have set some dedicated wake up pin aside HW flow control.

About pin 21, my recommendation would be to be as close as possible from our STEVAL-IDB008V1M eval kit. as can be seen here, pin 21 is linked to main ground through a 0Ohm resistor.

Regards

Laurent

[USuha.1]

Hi Laurent,

i am too facing the same kind of problem.

i want to connect the BlueNRG-M2SA with the mcu over uart. So my question is does BlueNRG-M2SA communicate over uart by default or we need to program it?

Right now i am using the usb to uart bridge to see the BlueNRG-M2SA behavior on COM port.

i have used spbt bluetooth module in my past projects and thinking that BlueNRG-M2SA will also work in same way.

Please guide.

Regards,

Utsav Suha