Interference caused by the STM nucleo h743 board even with the default blinking-led program?

[JSihv.1]

Hi, I'm using a STM32 H743ZI nucleo board as a platform for implementing battery BMS. I have been struggling with a interference on my setup which is distorting the voltage and current ADC measurements. I have been debugging the source of this interference and it turned out that this interference is caused by the nucleo board (or the H743 chip). I have come into this conclusion as the interference is even present when tested for a completely new nucleo board which has the default blinking-led program running without any codes uploaded through the CubeIDE or any other pins than the power input pins connected to the board. To demonstrate the problem, I have powered the board through the Vin pin with approximately 10V supplied by three series-connected Li-ion cells (not present in the figure) and inserted a oscilloscope probe between Vin and Gnd. The situation is illustrated below in Fig. 1 for a new H743 nucleo having that blinking-led default program. (never mind the resistor and cap on the breadboard as those are just providing a leads to put the probe leads into). As the board is powered form batteries, the input voltage should be very clean from the usual power supply noise and interference, but unfortunately, it is not.

Fig1

Now, when taking a closer look on the interference (or whatever you may call it), it is applying on every 18ms (Fig 2) and lasts about 2.2ms (Fig. 3), corresponding to 55Hz and approx. 450Hz, respectively. The interference has also repetitive sequence of varying amounts of 7.578kHz and 15.15kHz peaks (Figs 4 and 5). In this demonstration, the sequence of these interference bursts are as follows: 2 peaks of 15.15kHz, then 4 peaks of 7.51kHz, then 8 peaks of 15.1kHz and 7 peaks of 7.5kHz at the end. I have noticed that the sequence is not always like this but the peaks are always either 7.5 and 15kHz. Not to mention that this burst always comes on every 18ms and lasts for about 2.2ms.

Fig2.

Fig3.

Fig. 4

Fig. 5

For fun and for being desperate, I also tested whether the similar thing happens with a stm32 nucleo F411re which I have. It turns out that the interference is not present for that board as shown in Figs 6 and 7. The setup was exactly the same and the F411re also had its blinking led default program in it. The small deviation in the voltage is caused by the leds LD1 and LD2 blinking and, therefore, drawing current from the batteries which decreases the voltage.

Fig. 6

Fig. 7

 

So, I was wondering if anybody can help me with because I have no idea what the problem could be and how to get rid of this interference. I figure that the phenomenon is also present with other users as well using H743ZI nucleo because the problem is clearly related to the board or the chip. So far, I have not been able to come across any topics on here or anywhere else where this issue is addressed. However, as the problem is even present when running the default program, I hope that this issue is traceable and fixable.

Aloing with the batteries, I have used also the ST-link as a supply as well as other 5-12V power supplies connected either on Vin or EX5 pin. The same interference is present with them all. So the board is transmitting the interference to the circuit from a source which I do not know regardless of the power supply.

Thank you in advance for your cooperation!

[LCE]

If that Nucleo Board is very much like that for the STM32F7, then (I think, not so sure) there isn't any capacitor anywhere close to the connector pins where you connect the power supply.

That's one thing you should start with, place some 10µF ceramic cap somewhere close to the connector pins.

Anyway, the board with the STM32F7 (same Nucleo-144 ?) was made for basic functional evaluation.

I have looked at the PCB layout, and well, it would probably not pass an EMC test.

But that was a hard job, with the multi-function pins, and getting many of these over solder bridges to the connectors.

So I'm not surprised about these spikes - you didn't tell us about the voltage level, by the way. From the scope pics I guess it's somewhere below 1 mV ?

Whatever, try the cap.

And beware of ground loops, with the scope, a PC, the battery pack.

Next questions:

What is the firmware doing?

Does it go to sleep inbetween toggling the LED?

What is the ST-Link STM32 doing / how's it connected?

What's the clock source?

[AScha.3]

board should be ok :

but:

 

and dont forget : H7 are really fast switching chips, i see spikes up to 2.5 GHz when connecting wires to a fast output like SPI to display etc.

and board might have switching regulator, smps supply.

and H7 chips can have smps on chip also !

the "small" chips, like F411 all have linear regulators and so producing no spikes on supply line.

[JSihv.1]

Hi all,

Thank you for your answers, during the weekend, I discovered a solution for the problem from another topic on this forum.

https://community.st.com/s/question/0D50X00009sV2JSSA0/fluctuations-in-adc-value-of-stm32h743-mcu

It seems that the Ethernet port is constantly powered in the nucleo board which creates spikes and noise on the analog domain. By removing L1, the ethernet port and its ICs are disconnected form the board and the interference is gone. I do not know if there is a software option to do that but the hardware solution is enough for my purposes as I do not need the Ethernet PHY.