MB1641 - Nucleo STM32WB15CC slowness between BLE and UART

[Wiliam]

Hello! 

I have a Nucleo Board MB 1641 (STM32WB15CC) and I am developing an application using BLE, in P2P mode. Including based on the usage example provided by ST.

The application needs to transmit from the UART to the BLE and return the response from the BLE to the UART. However, it is noted that this "route" takes around 940ms. Analyzing, I observed that the problem may be at the UART (TX) output, as measuring the time from BLE output to buffer return, we have 140ms. In other words, the loss is located in the transfer from BLE to UART, in the return message to our devices. It turns out that our field devices (UART) have a listening time of 1s, and adding up all the time, we have 1020ms, meaning that the device does not receive the response.

I think the clue is in the sharing of the serial port by ST-LINK. I powered the board with a USB cable without communication pins (electric power supply only) and the problem persists. 

Could you, in your infinite kindness and wisdom, help me?

Grateful for the attention!

Wiliam (from Brazil)

[STea · Accepted solution]

Hello @Wiliam ,

i need to have more information about your configuration to further investigate on this matter :

• what UART instance are you using (UART1 or LPUART1)?
• Did you change the baudrate of the UART instance ?
• are you using DMA to do the UART transfer ?
• how are you measuring the latency ?

because all those modes can affect the latency of the transfer .

BR 

Hichem 

[Wiliam]

Dear STea,

The problem has been resolved.

There was a scheduled task on the Time Server slowing down the response time. This function was rewritten in another way and everything was normalize

I have other questions about this application (e.g. LPUart), but I will submit another post.

Thank you for your kind attention,

Wiliam