This is the documentation page for the SPI_PiPower and I2C_PiPower boards.
- 1 Overview
- 2 Use cases
- 3 Assembly instructions
- 4 External resources
- 5 Additional software
- 6 Pinout
- 7 jumper settings
- 8 Protocol
- 9 The software
- 10 Default operation
- 11 Future hardware enhancements
- 12 Future software enhancements
- 13 Changelog
This board enables you to switch upto 4 separete 12V 1A loads, and switch the 5V power rail to the GPIO header of the Paspberry Pi.
Electrically the PiPower has a few modes-of-operation.
Pipower powered from USB, powers RPi on command
In this configuration you can use your normal USB power supply, and when a time elapses power the 'pi up. Or you can have the pi power up when a signal on the inputs changes.
This is also the easiest way to provide the watchdog function.
Pipower powered from RPi. Switches 5-15V appliances on command
This is not the original purpose of the PiPower, but a nice extra. The PiPower can switch 1A loads.
Pipower powered from 7-15V on screw connector. Switches a load on command (usually DCDC converter powering PI)
This is the configuration best suited for battery power. The PiPower keeps time, and monitors up to two inputs and switches the 'pi on to handle things when either time runs out or one of the inputs becomes active. This way the PiPower can power up your 'Pi for short periods to do "complicated" stuff, while it conserves power for the long times of inactivity.
Pipower powered from 5V on screw connector
This is similar to the first item, but now you can use your own DCDC converter. The simplest DCDC converters still use a bit of "idle power", so it might not be as good as the "PiPower directly from the battery" case and having the PiPower turn on the power to the DCDC converter.
On the other hand, if you have a DCDC converter that is efficient at low loads and/or you need the DCDC converter to run anyway because of the other "input signals", then this mode is provided.
None: the board comes fully assembled.
Power input. Usually 12V. Do not apply 12V when jumpered for 5V on this connector as it will fry your PiPower.
Opto isolated input 0. Max 20V.
Opto isolated input 1. Max 20V.
The only LED is a power indicator.
See solder jumpers on how to change the solder jumper.
By changing the solder jumper SJ1, you can make the connector SPI1 into an ICSP programming connector for the attiny44 on the board.
JP1: Power source selection
1-2: RPi powered
2-3: USB or X1 powered
JP2: Vin selection
1-2: X1 powered, Vin = 5V
2-3: X1 powered, Vin > 5V
N-C: USB or RPi powered
For the intro to the SPI and I2C protocols read: SPI versus I2C protocols
The board specific protocol can be found here: PiPower_protocol
You should also read the General_SPI_protocol notes.
For arduino, a sample PDE is available, called ardemo_lcd.pde, also at the BitWizard software download directory .
This is a demo to send things using SPI to the lcd board. The SPI routines there are applicable for the PiPower board as well.
Future hardware enhancements
Future software enhancements
- Initial public release