# Mixed voltage interfacing with the Bus Pirate

(Difference between revisions)
 Revision as of 15:29, 20 August 2010 (view source)Ian (Talk | contribs) (→5.0volts)← Older edit Revision as of 15:30, 20 August 2010 (view source)Ian (Talk | contribs) (→Any voltage 1-Wire, I2C)Newer edit → Line 54: Line 54: ===Any voltage 1-Wire, I2C=== ===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 * 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''' * Open collector buses like 1-Wire and I2C '''always use pull-up resistors''' * These modes have no output configuration, outputs are always HiZ * These modes have no output configuration, outputs are always HiZ

## Revision as of 15:30, 20 August 2010

This will be an updated guide to using the Bus Pirate pull-up resistors to interface stuff at different voltages.

## Contents

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

• 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
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
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