Need STM32 GPIO operate on 1.8v

[bluenow1896]

Posted on August 03, 2017 at 20:26

Hi, recently in a project I need the GPIOs on STM32 to operate on 1.8v logic level. By quickly looking through datasheets, it seems many of STM32 can do so, for example, to STM32F407VG, if provide 1.8v to VDD, it runs GPIO on 1.8v level. However, I have difficulty to make such changes on TM32F4Discovery board, as there is no 1.8v power source available on the board.

Now I have the question, which ST Discovery board or Nucleo board can support &sharp1.8v GPIO easily? I want to try it out. I need the board support USB port as USB device, and run the GPIO on 1.8v, it would be better if it provides I2C slave interface on 1.8v also.

Thanks for your advice.

-Andy

#1.8v-gpio

[Tesla DeLorean]

Posted on August 03, 2017 at 21:04

USB won't work from a 1.8V supply. You'd need an L series part with a VDDUSB pin to power the transceiver.

When interfacing to 1.8V modules with the F2/F4 we use level translators, some TI part with 8 bidirectional channels as I recall.

[bluenow1896]

Posted on August 03, 2017 at 21:46

Thanks for reply. I'm not sure what do you mean 'USB won't work from a 1.8V supply'?  Do you mean that when provide VDD 1.8v to STM32F407VG, the USB interface on STM32F407VG wasn't work?

If I have to use a STM32L4xx , that is fine, let me know which Discovery board or Nucleo board be best for me for this prototype?  As I mentioned early, I need an USB device interface, 1.8v GPIO , and 1.8v I2C slave interface on the evaluation platform.

I will like to avoid to use extra circuit to do the level shift.

Thanks again.

-Andy

[Szymon PANECKI]

Posted on August 03, 2017 at 22:22

Hello Andy,

Looking at the requirement:

I need the board support USB port as USB device, and run the GPIO on 1.8v

it seems to me that maybe STM32L4 can be an interesting solution for you. STM32L4 in packages with big amount of pins (LQFP144, BGA132, CSP72 and CSP81) have VDDIO2 domain. This domain has a dedicated supply pin, which level can be in range of 1.08 ? 3.6V, comparing to VDD 1.71 ? 3.6V and VDDUSB 3 - 3.6V. VDDIO2 domain supplies only pins from GPOIOG, while VDD supplies rest of the GPIOs. With this solution you can easily get a voltage level tranlator or pins operating on different voltage levels.

Regarding the evaluation boards with STM32L4: you can use

http://www.st.com/content/st_com/en/products/evaluation-tools/product-evaluation-tools/mcu-eval-tools/stm32-mcu-eval-tools/stm32-mcu-nucleo/nucleo-l496zg.html

, as it offers STM32L496 in LQFP144 package. Unfortuantely VDDIO2 on this board is connected to VDD, so you would need to cut a wire and make hardawre modification on your own.

Regards

Szymon

[S.Ma]

Posted on August 03, 2017 at 22:12

Start from looking at the STM32L4 family. It has separated USB, VDDIO1 and VDDIO2 supplies which would enable a rich mix of diverse supply voltages to coexist. For each group of GPIO supply voltage there are the usual serial interfaces suspects. This way, external voltage shifters might be avoided.