RAK4200 Floating Pins During Sleep

LPWAN Modules / EVBs
#1

Putting RAK4200 into sleep doesn’t get the module into the sleep current as advertised.
It is around 40 uA. Upon checking all the pins on RAK4200 during sleep, I notice the following pins are floating during sleep:

  • 3 - UART2_DE
  • 4 - UART1_TX
  • 6 - UART1_DE
  • 9 - I2C_SCL
  • 10 - I2C_SDA
  • 16 - SPI_MISO

But, the biggest culprit among them is pin 16 (SPI_MISO). If I were to put a multimeter to measure the voltage of this pin 16, the extra 40 uA will disappear. Firmware revision is v3.0.12.

#2

Hi @phangmoh, How do you test the module current? Separate module test, or module + your circuit board test?

#3

Hi @Sucre, module + board. Prior to this, RAK4200 was not mounted to ensure nothing is wrong with circuits. Base board current is 7 uA. Adding the RAK4200 shoot up to more than 50 uA. Those RAK4200 pins (3, 4, 6, 9, 10, 16) I mentioned are not connected to anything on the board as they are not needed. The fact that they have voltages other than GND and 3.3V, it means they are floating.