Mixed voltage interfacing with the Bus Pirate
This will be an updated guide to using the Bus Pirate pull-up resistors to interface stuff at different voltages.
The Bus Pirate's on-board pull-up resistors can be used to interface electronics above and below the Bus Pirate's 3.3volt supply.
Read how the pull-up resistors on the Bus Pirate work.
Read our guide to pull-up resistors and high impedance pins.
Here's some examples of how to interface different voltages using the Bus Pirate.
Interface directly with normal pin outputs.
Any voltage 1-Wire, I2C
The Bus Pirate can interface with 1-Wire or I2C at 5.5volts or less.
Open collector buses like 1-Wire and I2C always use pull-up resistors.
If you use the Bus Pirate's on-board pull-up resistors, remember to connect the Vpullup pin to the test circuit supply voltage. The Bus Pirate pull-up resistors are powered through the Vpullup pin.