Skasi7
Posts: 2
Joined: Wed Mar 07, 2018 11:28 am
Location: San Jose,CA,USA

Logic level translator 1V8 MEMS Sensor RPI compute module

Tue May 08, 2018 7:33 pm

Hi,

I am interfacing a MEMS sensor with the RPI compute module 3 - FIS1100 from ON Semi
The logic level for this IC is 1.8V.Do I have to use a IC like TI TXB0108 bidirectional Level Translator(1.8-3.3V) to communicate with the PI via SPI?

FIS1100- https://media.digikey.com/pdf/Data%20Sh ... asheet.pdf
FIS1100.png
FIS1100.png (78.25 KiB) Viewed 419 times
I am interfacing with a raspberry Pi compute module 3 and in the schematic for the IO board I see voltage select bank 0/1 for 3.3 and 1.8V what is the purpose of this voltage select header?
io board.png
io board.png (62.11 KiB) Viewed 419 times
Do I have to use a level translator ?


~Skasi

KnarfB
Posts: 194
Joined: Wed Dec 14, 2016 10:47 am
Location: Germany

Re: Logic level translator 1V8 MEMS Sensor RPI compute module

Wed May 09, 2018 4:08 pm

If you set the jumper to 1V8 the corresponding group of GPIO pins will have 1.8 V levels, and you dont need a level converter.
See here for some explanation: http://www.seeedstudio.com/document/pdf ... uction.pdf
Only change the jumper settings when completely switched off.
The only caveat is, that the GPIO levels can only be set in 2 large GPIO groups.
If you have other 3.3V peripherals connected, you have to split the GPIOs accordingly.

Skasi7
Posts: 2
Joined: Wed Mar 07, 2018 11:28 am
Location: San Jose,CA,USA

Re: Logic level translator 1V8 MEMS Sensor RPI compute module

Thu May 17, 2018 12:01 am

Hi,

Thank you for answering my question.I will have to use a 3.3V logic as Vref for IO for the compute module to work with other peripherals I am interfacing.
Do I have to use a logic level translator if I use 3.3V logic or can the raspberry pi recognize 1.8V as a low threshold without a logic level converter?

Regards,
Skasi

es_pi_user
Posts: 6
Joined: Tue May 15, 2018 11:00 am

Re: Logic level translator 1V8 MEMS Sensor RPI compute module

Thu May 17, 2018 12:49 pm

Skasi7 wrote:
Thu May 17, 2018 12:01 am
Hi,

Thank you for answering my question.I will have to use a 3.3V logic as Vref for IO for the compute module to work with other peripherals I am interfacing.
Do I have to use a logic level translator if I use 3.3V logic or can the raspberry pi recognize 1.8V as a low threshold without a logic level converter?

Regards,
Skasi
According to the datasheet the absolute maximum IO Leves of the Sensor is 2.05V so you should use a level translator because the Raspi will drive the lines with 3.3V.

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