The Bus Pirate has a ‘Programmable Power Supply Unit’ (PPSU) that can power devices from the VOUT/VREF pin of the main connector.

  • 1-5volts adjustable output, 400mA max
  • 0-500mA current sense
  • 0-500mA current limit with digital fuse
  • Backflow prevention to protect the PPSU when an external voltage is applied to the VREF/VOUT pin

Enable

Bus Pirate [/dev/ttyS0]
I2C> W
Power supply
Volts (0.80V-5.00V)
x to exit (3.30) > 5
Maximum current (0mA-500mA), <enter> for none
x to exit (none) > 100
5.00V requested, closest value: 5.00V
100.0mA requested, closest value: 100.0mA

Power supply:Enabled
Vreg output: 5.0V, Vref/Vout pin: 5.0V, Current: 3.0mA

I2C>

Type uppercase W followed by enter to enable the power supply.

  • Enter the desired output in volts, for example 5 followed by enter.
  • Enter the desired current limit in milliamps, for example 100 followed by enter.

The Bus Pirate will calculate the closest possible values and enable the PPSU.

Quick enable

Bus Pirate [/dev/ttyS0]
I2C> W 5 100
5.00V requested, closest value: 5.00V
100.0mA requested, closest value: 100.0mA

Power supply:Enabled
Vreg output: 5.0V, Vref/Vout pin: 5.0V, Current: 2.3mA

The W command accepts voltage and current as command line options.

  • The first parameter specifies the voltage
  • The second parameter specifies the current limit (omit for no current limit)
Bus Pirate [/dev/ttyS0]
I2C> W 5
5.00V requested, closest value: 5.00V
Current limit:Disabled

Omit the second parameter to disable the current limit fuse.

Check voltage and current

Check the voltage and current in the live view statusbar if active, or show the power supply voltage report using the v command followed by enter.

  • The top line indicates the power supply is set at 5.0 volts with a 100mA current limit.
  • The third line shows that 2.1mA is being consumed on VOUT/VREF. Since nothing is connected this is the current leakage, offset error and noise in the RP chip’s analog to digital converter.
  • The last line shows that VOUT currently measures 5.0 volts, and all IO pins measure 0 volts.

Current limit

Bus Pirate [/dev/ttyS0]
Error: Current over limit, power supply disabled

I2C>

When the programmed current limit is exceeded the PPSU hardware fuse disables the power supply.

  • The terminal colors invert repeatedly.
  • An alarm bell sounds
  • An error message is shown
  • Command execution is halted.

Use the W command to restart the PPSU again.

Disable

Bus Pirate [/dev/ttyS0]
I2C>w
Power supply: Disabled
I2C>

Lowercase w disables the PPSU.