How to properly connect the X-Nucleo-LPM01A to a nucleo-L152RE (GPIO not working)

[OØgar.1]

Hello!

I'm trying to power only the mcu on a nucleo-L152RE dev-kit from the X-nucleo-LPM01A to measure it's power consumption, however i suspect the mcu is not running, and debugging it provides wierd results that I cant make sense of.

The program I'm trying to run is as simple as it gets: the onboard LED toggles on and off with a delay of 3000 ms. When powering the board from USB (debugger & mcu powered), everything works fine.

The issue arise when I try to disable the debugger and only power the mcu from the X-nucleo. I do this by connecting CN14 pin 1 (GND) and CN14 pin 3 (VOUT (+)) on the X-nucleo to GND and VDD (pin on JP6, IDD) on the dev-kit, respectively.

In this configuration, the x-nucleo report a current draw of about 1mA, however the LED is not blinking.

I've followed the exact steps in the community post explaining this ("How to connect my stm32 to the x-nucleo-lpm01a"), read the user manual for the X-nucleo (UM2243) and nucleo-L152RE (UM1724) thoroughly, inspected the schematics (C-04 version, MB1136) and read other sources i found, to no avail.

Here are a few comments about what I've tried, and the results I got:

• Powering the dev-kit from USB with JP5 (U5V/E5V selection) and JP6 (IDD) removed, the mcu still runs, and the LED is blinking, although dimmer. This is what confuse me the most. According to schematics, this should leave +3v3 and VDD at 0V, but I read around +1.9V.
• I've tried with JP5 on and off - no difference.
• I've tried removing SB12 (NRST from mcu to debugger) and SB2 (3v3 reg output to JP6, IDD) and powered through +3V3 pin instead (JP6, IDD connected). This is specified in the UM1724 dev-kit manual, but it makes no difference - the LED is still not working.

I feel like I've tried anything at this point, but it's still not working. Can anyone help me understand why this isn't working?

[Foued_KH]

Hello @Oscar Øgar Meisal​ ,

Please check this User Manual : STM32 Nucleo expansion board for power consumption measurement

Foued

[OØgar.1 · Accepted solution]

I found the issue, but I'll leave this open for others:

1. Had to remove SB50 & SB16 to disconnect the clock signal from the st-link debugger mcu to the STM32L152 mcu. Also had to switch to the internal high speed clock (HSI), as there are no external clocks on the board by default.
2. SB12 had to be removed to completely disconnect the NRST of the STM32L152 mcu from the st-link debugger mcu. Prior to doing this, the NRST pin was at around 1.8V, however when removing SB12, NRST was at 3.3V.