7 Replies Latest reply on Jan 31, 2016 7:30 AM by Bob_Denver

    Suggestions for level shifters to use with mini breakout board

    KurtE

      I know that I have been frustrated a few times, when I have tried to hook up something like an TFT display to the mini breakout board and I know that I need to use some level shifter, to make the device compatible with the 1.8v IO pins of the Edison.    I have literally tossed a couple of the level shifters in the trash.

       

      I know that I am not alone, as Paul (the owner) of PJRC (Teensy) I posted recently: PJRC (Teensy) Forum

       

      I know that it took me a lot longer than it should have to get the Adafruit TFT display to work.  Partially because of the level converters, and partially as I ran into some issues about some IO pins appear to kill networking or ... which I posted in a different thread.

       

      On my Breadboard that I was able to get the display to work I am using one of the Adafruit shifters that uses the TXB0108 (8-channel Bi-directional Logic Level Converter [TXB0108] ID: 395 - $8.00 : Adafruit Industries, Unique & fun DIY electro…) which worked.  But these drivers are not perfect as they can drive very little.  Earlier I tried their converters that they say is good for I2C 4-channel I2C-safe Bi-directional Logic Level Converter [BSS138] ID: 757 - $3.95 : Adafruit Industries, Unique & fun DIY…  and OK for SPI... and did not have any luck.  Again Paul of PJRC confirmed this as well.

       

      Also secondary note on shifters.  It appears like choosing the right voltage pin out of the mini board is important.  There is no 5v pin, but there is one that could get something like 4.x volts.  I tried and display did not work, I switched to the 3.3v pin and it worked...  Wish mini board exported 5v pin from voltage converter.

       

      Question: What voltage level shifters have people had good luck with.  I totally understand that this is probably not a one size fits all answer.  Could for example have different answers for:

      a) SPI - bidirectional?  unidirectional?

      b) I2C

      c) high speed bidirectional versus unidirectional?

       

      Thanks