Mixed voltage interfacing with the Bus Pirate
From DP
This will be an updated guide to using the Bus Pirate pull-up resistors to interface stuff at different voltages.
Contents |
About
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.
Examples
Here's some examples of how to interface different voltages using the Bus Pirate.
These examples assume you use the Bus Pirate on-board pullup resistors. If you use the Bus Pirate's on-board pull-up resistors, remember to connect the Vpullup pin to the circuit supply voltage. The Bus Pirate pull-up resistors are powered through the Vpullup pin.
Some modes (1-Wire, I2C) only use high impedance pin outputs
3.3volts
Select output type:
1. Open drain (H=Hi-Z, L=GND)
2. Normal (H=3.3V, L=GND)
(1)> 2
Ready
- Interface directly with normal pin outputs
- No pull-ups or Vpullup pin connection used
5.0volts
Select output type:
1. Open drain (H=Hi-Z, L=GND)
2. Normal (H=3.3V, L=GND)
(1)> 1
Ready
SPI> W
Power supplies ON
SPI> P
Pull-up resistors ON
- Connect the Vpullup pin to the power supply of the 5volt circuit
- Choose Hi-Z output type
- Enable the on-board pull-up resistors
- The 5volts can come from the Bus Pirate or an external supply
2.5volts
Select output type:
1. Open drain (H=Hi-Z, L=GND)
2. Normal (H=3.3V, L=GND)
(1)> 1
Ready
SPI> P
Pull-up resistors ON
- Choose Hi-Z output type
- Connect the Vpullup pin to the power supply of the 2.5volt circuit
Any voltage 1-Wire, I2C
I2C> P
Pull-up resistors ON
- 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
- These modes have no output configuration, outputs are always HiZ