use the EH pin of ST25DV for low-power MCU (stm32L4)

[Schuyler]

I want to use the EH pin of ST25DV to obtain energy through RF and power supply data transmission for low-power MCU (stm32L4). Can this scheme be realized? What should I do?

[Rene Lenerve · Accepted solution]

Hi @帅 罗​​,

This can be done by connecting the EH pin to the VCC of the STM32L476. Don't forget to connect the ground of the ST25DV and of the MCU. If you want to communicate through I²C between MCU and ST25DV you will also need to connect the VEH of the ST25DV to the VCC of the ST25DV. Take into account that the current provided by the EH pin will be limited by the field provided by the RF.

You will find some documentation on Energy Harvesting with the following documentations:

ST25DV DataSheet

AN4913: Energy harvesting delivery impact on ST25DV-I2C Series

AN5233: Energy harvesting with ST25DV-I2C series Dynamic NFC Tags

Kind Regards.

[Schuyler]

Hi,@Rene Lenerve​ 

Thank you for your reply. As far as I know, EH output in ST1 is AC, and the energy collected only through RF is less than 10mw. So if I connect EH and 3.3V with a wire, will MCU be driven to run? MCU does not carry out USB power supply only through EH's energy.

Kind Regards.

[Rene Lenerve]

Hi @帅 罗​,

I'm not sure to understand exactly what you mean.

As you said the power provided by the EH pin is limited, so you will not be able to power supply every system. You can only use this pin for a system that needs less than 10 mW. An MCU can run with a lower frequency to consume less energy, and for example the L476 can run in low power mode.This is something working and feasible but only for low power systems.

Hope this will help you.

Kind Regards.

[Schuyler]

Hi,@Rene Lenerve​ 

As you see, an MCU can run with a lower frequency to consume less energy, and for example the L476 can run in low power mode. So what is the power consumption of the stm32l476rg, and if I use EH's energy to power the MCU and then do sensor testing, what should I do?

Kind Regards.

[Rene Lenerve]

Hi @帅 罗​​,

• So what is the power consumption of the stm32l476rg

Read the reference manual (or DataSheet) of the STM32L476, it depends on how you configure it you can have various consumption. And then write the source code to configure the STM32 according to your needs. If you need support for that open a thread in the STM32 section.

• if I use EH's energy to power the MCU and then do sensor testing, what should I do?

You can do whatever you want for your application, I guess read the sensor and write information to the ST25DV. It's up to you to develop the code for this and you probably already have some of it.

Kind Regards

[Schuyler]

Hi,@Rene Lenerve​ 

Thanks for your reply! Code communication is later, I think the first thing to solve the problem is how the energy output from EH can power the STM32L4 and make the MCU work properly. I need L4 to collect temperature with SPI and transmit it to ST25 with i2c, but I need MCU to collect and test only with EH's energy. So what should I do with the EH pin to power the MCU?

Kind Regards

[Berenice BENVEGUDA]

Hello @帅 罗​​,

Please read first answer given by Rene, all info you need is in his first post.

Best Regards,

BB

[Schuyler]

@Berenice BENVEGUDA @Rene Lenerve 

I need to use NFC07A1 to power STM32l476RG, but the PIN 4 connecting CN6 according to the instructions failed to make the MCU run. I tried to write the LD2 flicker program, but the NFC power did not make the LD2 flicker after the USB power failure. But the LD3 power indicator of my L4 was already on, so why didn't I succeed in getting the MCU wirelessly powered? According to the instructions I find that the LD3 works as long as it is successfully lit. What do I need to do to make the EH output pin power the L4 operation?

[JDEME]

Hello,

Some tricks:
Basically, as already mentioned, the initiator field (reader ?) must be strong enough for powering for the STM32L476.
If the EH is used the X-NUCLEO-NFC07A1 ST1connector jumper must be correctly set.
It is recommended to populate C5.
Multiple powering requires arbitrations, for only VEH.
On the Nucleo mother board the powering must be disconnected ( SB2)
To avoid powering IOs conflicts the tracks coming from the embedded ST-Link must be disconnected (card breakable)

Regards,