Because the Arduino and Basic Stamp are 5V devices, and most modern sensors, displays, flash cards and modes (including the Raspberry Pi) are 3.3V-only, many makers find that they need to perform level shifting/conversion to protect the 3.3V device from 5V. The Adafruit 8-Channel I2C Bi-Directional Logic Level Converter is able to convert signals from 5V down to 3.3V (and vice versa) meaning you can safely use 5V or 3.3V devices with the Raspberry Pi!
Although one can use resistors to make a divider, for high speed transfers, the resistors can add a lot of slew and cause havoc that is tough to debug. For that reason, we like using 4050/74LVX245 series and similar logic to perform proper level shifting. Only problem is that they are only good in one direction which can be a problem for some specialty bi-diectional interfaces and also makes wiring a little hairy.
That’s where this lovely chip, the TXB0108 bi-directional level converter comes in! This chip performs bidirectional level shifting from pretty much any voltage to any voltage and will auto-detect the direction. Only thing that doesn’t work well with this chip is i2c (because it uses strong pullups which confuse auto-direction sensor). If you need to use pullups, you can but they should be at least 50K ohm – the ones internal to AVRs/Arduino are about 100K ohm so those are OK! If you don’t want to worry about directional pins this is a life saver!
This breakout saves you from having to solder the very fine pitch packages that this chip comes with. We also add 0.1uF capacitors onto both sides and a 10K pull-up resistor on the output enable pin so you can use it right out of the box!
The Adafruit 8-Channel Bi-Directional Logic Level Converter Features:
- Level shifts to protect the 3.3V device from 5V.
- TXB0108 bi-directional Level Converter.
- Fully Assembled and Tested PCB with 8 Full Bi-Directional Converter Lines
- Auto-Detects Voltage Level Direction
- Comes complete with 2 x 6-Pin Headers which can be soldered on for breadboarding
- 0.1uF Capacitors on both sides of chip and a 10K pull-up resistor on the Output Enable Pin
TXB0108 App Note (Explains Function)