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

[Jay_Bolboli]

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

[RomainR. · Accepted solution]

Hi @Jay_Bolboli 

Can you refer to UM2243 Rev 2 in chapter 8.2 Settings for use of the Arduino Nano connectors in a
Nucleo32 use case.

You do not have to unsolder/solder SB14 and SB9. Let these solder bridge shorted as default.
Nucleo32 board is powered trough AREF (which is same than VDD)

- Simply remove JP1 on Nucleo32 to prevent reverse voltage from X-Nucleo-LPM01A to U3 LD39050.
- Insert Nucleo-L432KC on header CN12/CN13 on  X-Nucleo-LPM01A.
- Connect COM port with STM32CubeMonitorPower, Take Control then check Input Voltage(mV) = 3300mV
- Connect Nucleo-L432KC STLink to your computer.
- Set Acquisition Time(s) = Infinite and then Start Acquisition with STM32CubeMonitorPower.
Now you can program/debug your firmware and monitor the power consumption. 

Let me know if it helps?

Best regards,

Romain,

[Jay_Bolboli]

Hi @RomainR.  

Thank you for your prompt response and help.

You're correct, I followed your instructions and it worked. However, I have encountered an issue with my sensors, Tx, and RX, which are connected to peripherals like SPI and UART—they have stopped working.

I suspect this might be because the method I used is for measuring the power consumption of the MCU alone, given that JP1 is open.

Could you please provide some advice on how to resolve this issue?

[Andrew Neil]

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@Jay_Bolboli wrote:

Each time, I have to solder them again, program the board, and then open the solder bridges SB14 and SB9.

---

No, you don't have to keep soldering & unsoldering them!

Just unsolder them, and then use jumper wires to make the connections when you need them.

Be sure to check carefully with the schematic - don't trust just the Manual - that there are no other connections to the ST-Link or other stuff. Otherwise these will contribute leakage to your measurements...

[RomainR.]

I don't know exactly your application, what is the power source for your sensors? Is it present all the time, what do you measure?
Please give more details otherwise I wouldn't be able to help you!

Best regards,

Romain

[Andrew Neil]

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@Jay_Bolboli wrote:

Hi @RomainR.  

I suspect this might be because the method I used is for measuring the power consumption of the MCU alone, given that JP1 is open

---

So check the schematics - they will show you how power is routed.

As @RomainR. said, we have no idea what your sensors are, nor how you have them connected - so can't possibly comment on what might be going wrong.

You need to give more details - preferably a block diagram and/or schematic of your setup.

Some good, clear photos may also help.

[Jay_Bolboli]

Dear @RomainR. 

Simply I can say that the application continuously measures CO2 and tVOC every second using a sensor connected to the board via I2C1. This sensor is powered by the 3.3V pin.

The gathered sensor data is then transmitted using two different communication methods:

1. It is transmitted through the LoRa module, which is connected to SPI1 and powered using the 3.3V pin.
2. It is also transmitted through an optical Tx module connected to UART1 Tx, powered by the 5V pin.
   
   Thanks for your help and support

[Andrew Neil]

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@Jay_Bolboli wrote:

This sensor is powered by the 3.3V pin.

---

So look at the schematics to see what powers that 3.3V pin. That will show you whether the pin receives your power from the X-Nucleo-LPM01A.

---

@Jay_Bolboli wrote:an optical Tx module connected to UART1 Tx, powered by the 5V pin.

---

Again, look at the schematics to see what powers that 5V pin

EDIT

The X-Nucleo-LPM01A only supplies up to 3.3V - so it's not going to power 5V:

https://www.st.com/en/evaluation-tools/x-nucleo-lpm01a.html 

[RomainR.]

For sensor powered with 3.3V and when STLink is powered.
Even if you removed JP1, 3.3V should be still present . But only if you solder properly SB14.

Then +5V is normally also present.

Did you measure them?

Best regards,

Romain

[Jay_Bolboli]

Dear @RomainR. @Andrew Neil 

Thank you for your help and time. 

I understand your points. 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.

In  UM1956 Rev 5, section 6.7, Hardware layout and configuration, it is mentioned that: 

----------------------

JP1 on: STM32 is powered (default)
JP1 off: an ammeter must be connected to measure the STM32 current
If there is no ammeter, STM32 is not powered.
----------------------
So I think this is because VDD is out . And I think the VDD is the main supply voltage that powers the core and peripherals.

I also connected a logic analyzer to check their signals, and I found that their signals (UART, SPI, and I2C) are available only if JP1 is connected.

FYI:
this is pinout, I took it from CUBEMX that shows how everything is connected. Furthermore, SB14 is closed, while SB16 and SB18 are open for I2C use.

Thanks again for your help, 
Kind regards