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Topic: Raspberry Pi Level Shifters and Monitoring (Read 2570 times) previous topic - next topic

Raspberry Pi Level Shifters and Monitoring

Long time reader, first time poster, great forum here!

I would like to introduce my first Raspberry board: a GPIO bi-directional level translator (3.3V <-> 5V):

- This is an in-between expansion board that you plug in the RPi P1 connector which gives a bi-directional level shifter for each GPIO (x 17)

- The board also acts as a monitoring as each GPIO has it's own LED for visualization of its state. The LEDs are buffered meaning that they don't have any influence on devices you may connect to the GPIOs

- Finally, there is a mini (micro!) prototype area with replication of the 5V GPIO

Here are a couple of pictures:
https://www.dropbox.com/s/jhk4aq6psx2qt ... 20wRPi.JPG
https://www.dropbox.com/s/dnkpsnjnpmm65 ... ments3.PNG

And my blog: http://stuff4pi.wordpress.com/

Let me know what you think about this board and if you have any comments or added features you would like me to put on the next revision.

I also put my extra boards on Tindie: https://www.tindie.com/products/Stuff4P ... onitoring/

Re: Raspberry Pi Level Shifters and Monitoring

Reply #1
Hi

Pretty cool board :p

I was wondering... Is this kind of level translator suitable for high speed signals? Usually, it works well with I2C buses (400khz), but does it support higher frequencies (SPI @20MHz)?

For your next revision, may I advice you to add a small RS232 converter (e.g. MAX232, if it still exists); personnaly, I still use this good'old bus (mainly for debug purposes), it is so simple and reliable... Or am I too much 'old school' ?
Maybe you could also put some TVS diodes, but I'm not sure if it is relevant here...

Regards

Re: Raspberry Pi Level Shifters and Monitoring

Reply #2
Thanks herpderp for the comments. The board works with I2C and SPI but I still need to figure out what is the maximum SPI clock possible.

Yeah, RS232 is very old school now ;-). I think I will develop soon a dedicated "communication" RPi expansion board with RS232, RS485 and USB. I was thinking of routing the I2C signals to a RS485 transceiver to allow different sensors to be located far from the RPi.