B-WL5M-SUBG1 (STM32WL5MOC) current consumption too high

[JBive.1]

Hello,

We have an issue with the B-WL5M-SUBG1 evaluation board: The idle current consumption is higher than expected: 89 uA (vs. expected: 1-2 uA) after joining (OTAA) successfully.

• Board: B-WL5M-SUBG1
• Firmware: STM32CubeWL/Projects/B-WL5M-SUBG1/Applications/LoRaWAN/LoRaWAN_AT_Slave and STM32CubeWL/Projects/B-WL5M-SUBG1/Applications/LoRaWAN/LoRaWAN_End_Node
• Firmware version: STM32CubeWL V1.3.0 (latest from https://github.com/STMicroelectronics/STM32CubeWL)
• Power supply: 5 V via USB-C adapter board
• Current measurement: STM32WL5MOC, not including sensors, measured at IDD jumper (JP2) using Joulescope

Do you have an idea what could be the issue?

Thanks!

[STTwo-32]

Could you please add the details of the configurations that you are doing.

Best Regards.

STTwo-32

[JBive.1]

Hi, steps to reproduce the issue:

• Firmware: Clone from https://github.com/STMicroelectronics/STM32CubeWL, import project "LoRaWAN_AT_Slave" into STM32CubeIDE, compile "Debug" using STM32CubeIDE.
• Connect debugger (STLINK-V3PWR) to board (B-WL5M-SUBG1), flash firmware to STM32WL5MOC.
• Command to LoRaWAN_AT_Slave application: AT+JOIN=1 (OTAA join).
• Wait until it has joined.
• Measure current consumption of the board over jumper JP2 (IDD) -> 89 uA.
• Same current consumption has been measured with the application "LoRaWAN_End_Node" (change in file sys_conf.h: SENSOR_ENABLED = 0).

Thanks!

[alexemdesgagne · Accepted solution]

Hi,
To resolve this issue, we pull the UART TX and RX pins high.

Maybe that could help you.

Alexandre

[JBive.1]

Hello Alexandre,

Thank you very much for your hint, you nailed it!

We changed two things:

• Pull-up on UART RX (PA3)
• Pull-down on JTDI (PA15)

This way, the idle current consumption went down to 1.9 uA! We are very happy with this.

Details:

Projects/B-WL5M-SUBG1/Applications/LoRaWAN/LoRaWAN_AT_Slave/Core/Src/usart.c: change:

    GPIO_InitStruct.Pin = USARTx_RX_Pin|USARTx_TX_Pin;
    GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
    GPIO_InitStruct.Pull = GPIO_PULLUP; // <-- changed
    GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_VERY_HIGH;
    GPIO_InitStruct.Alternate = GPIO_AF8_LPUART1;
    HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);

Projects/B-WL5M-SUBG1/Applications/LoRaWAN/LoRaWAN_AT_Slave/Core/Src/gpio.c: add in function MX_GPIO_Init():

  /* Configure GPIO pin : JTDI */
  GPIO_InitStruct.Pin = GPIO_PIN_15;
  GPIO_InitStruct.Mode = GPIO_MODE_INPUT;
  GPIO_InitStruct.Pull = GPIO_PULLDOWN;
  HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);

The same changes can be applied to Projects/B-WL5M-SUBG1/Applications/LoRaWAN/LoRaWAN_End_Node as well.

Thanks again!

[alexemdesgagne]

Excellent!

Happy to hear this news!

Alexandre