Using X-Nucleo-LPM01A for measuring power consumption of NUCLEO-L432KC

Jay_Bolboli · ‎2024-04-14

Hello Everyone,

For a project, I'm using a NUCLEO-L432KC board and it is connected to external sensors, Tx, and Rx (which work with 4-5 V). I want to use an X-Nucleo-LPM01A to measure its power consumption.
Based on the NUCLEO-L432KC documents, I have to open SB9 and SB14, then NUCLEO-L432KC can be powered on by X-Nucleo-LPM01A then we can measure the board power consumption.

But there is a problem. if I use this method I can't use ST-LINK and USB to program the NUCLEO-L432KC board and I can't change some parts of the code. Each time, I have to solder them again, program the board, and then open the solder bridges SB14 and SB9.

Now the question is, is there any alternative solution?

I really appreciate your help

Andrew Neil · ‎2024-04-16

@Jay_Bolboli wrote:
What I gather from what you're saying is that even when JP1 is open, it will not affect other peripherals. However, I believe it does affect them.

There may be some confusion on what you mean by "peripherals" here?

As you can see from the schematics, VDD is indeed the power supply to the STM32 Target chip; that will include power to all the STM32's internal peripherals - UART, SPI, I2C, etc.

But power to external peripherals - such as your LoRa and Optical Tx - will depend on how, exactly, you are powering those devices.

Again, you really need to provide a schematic of your system - showing how you have all these things connected.

Words/text are a particularly poor way to describe electrical connections - especially with language differences. This is why we use schematic diagrams!

Jay_Bolboli · ‎2024-04-16

Thanks Andrew.

I have provided a photo below that shows all the connections.

Reds are the power lines and blues are the signal lines.
Also, I have to mention that I tested the system. when JP1 was not connected signal lines did not work (I checked with a logic analyzer) but power was available. And when JP1 was connected everything worked fine.

Clock Configuration (I used MSI):

Kind regards,

Andrew Neil · ‎2024-04-16

So your power supply scheme looks like this:

Your LoRa, Sensor, and Optical TX are always & only supplied from the Nucleo
Your STM32 is supplied from the board when JP1 is fitted, but is must be separately supplied when JP1 is removed (or an ammeter needs to be inserted).

@Jay_Bolboli wrote:
I tested the system. when JP1 was not connected signal lines did not work (I checked with a logic analyzer) but power was available.

What do you mean by "power was available" there?

As you can see from the above diagram, power comes from three different places - they need to be all available for the system to work.

Jay_Bolboli · ‎2024-04-16

Yes, your diagram is correct.

LoRa, Sensor, and Optical TX are connected to +3v3 and +5V pins
STM32 also is supplied from X-Nucleo-LPM01A using AREF pin

All three power sources are available for the system (I have checked the pins using a multimeter).
however, I am not sure if the AREF pin is internally connected to smt32 or not. Based on the diagram it is connected and there is no bridge and it is connected to AVDD directly.

What do you mean by "power was available" there?

Here I meant that electrical power was flowing through the system (I have checked using a multimeter)

Thanks for your time and help

Andrew Neil · ‎2024-04-16

@Jay_Bolboli wrote:
STM32 also is supplied from X-Nucleo-LPM01A using AREF pin

Why not apply it at the VDD side of JP1 ?

Note that you'd also need to link the X-Nucleo GND to the L432KC GND

@Jay_Bolboli wrote:
I am not sure if the AREF pin is internally connected to smt32 or not. Based on the diagram it is connected and there is no bridge and it is connected to AVDD directly.

Yes, it is connected via SB10 and the L1 ferrite bead - which is there to filter digital noise from the analogue supply.

You are effectively feeding the power from the "wrong" side of the filter.

Jay_Bolboli · ‎2024-04-16

Hello @Andrew Neil @RomainR.

I want to thank you both for your help and support.

It appeared that the problem was the AREF. It was provided by the X-Nucleo-LPM01A, and I was able to measure it on the pin.

However, I discovered that internally, the AREF wasn't connected to MCU. I suspect this might be due to the ADC. In my application, I'm using the ADC, so it's likely that the AREF was being utilized as the reference voltage for the ADC. When I tested it without the ADC, the problem was solved.

Kind regards,