govattu

Golang library (or just simple wrapper) for accessing /dev/mem features on raspberry pi

based on wiringPi (http://wiringpi.com/) and http://www.airspayce.com/mikem/bcm2835/ Butchered go-rpio library and mutilated to this library with added features https://github.com/stianeikeland/go-rpio Feel free to merge hardwarePWM feature to go-rpio if my API design sucks.

Features

• GPIO input/output
• GPIO events rise/fall/level/asyncrise/asyncfall -Nice to use with command buttons, can do without aggressive polling
• HardwarePWM
  • only PWM0 tested

Features to do

• Raspberry jams with /dev/gpiomem when writing to mempwm[PWMMEM_RNG1] Before solving problem, run this as root (sudo)
• Multiple pin reads and writes. For parrallel interfacing LCDs etc...

Design principles

• No c code, no external dependencies
• This library contains only tricks that are not implemented with drivers like UART or I2C or SPI
• Only low level functionalities, no lcd functions or software pwm. They are implemented on higher levels
• API is going to freeze, but not yet

Pin numbering

Govattu uses so called BCM numbering. BCM and GPIO numbers go with same way

How to use

import "github.com/hjkoskel/govattu"

Initialize

hw, err := govattu.Open()

For creating unit tests or mocups there is inteface called Vattu and DoNothingPi example implementation

Basic gpio functions are

hw.PinClear(pin uint8) //for output 0
hw.PinSet(pin uint8) //For output 1
hw.ReadPinLevel(pin uint8) bool  //For input
hw.PullMode(pin uint8, pull PinPull) //Set pin pullup setting  govattu.PULLoff  or govattu.PULLdown or govattu.PULLup

Setting up hardwarePWM. If calculating divisors and ranges is hard. Please check simple example project https://github.com/hjkoskel/pipwm

hw.PinMode(18, govattu.ALT5) //ALT5 function for 18 is PWM0
hw.PwmSetMode(true, true, false, false) // PwmSetMode(en0 bool, ms0 bool, en1 bool, ms1 bool)   enable and set to mark-space mode for pwm0 and pwm1
hw.PwmSetClock(divisor uint32)  //Set clock divisor
hw.Pwm0SetRange(ra uint32) //SET RANGE
hw.Pwm0Set(r uint32) //Set pwm

This library also have function for setting events flags. Very usefull if code monitors button presses. It is handy to detect fall event and later check "did events happend"

hw.ZeroPinEventDetectMask() //At initialization
/*
Possible flags (bitwise or together)
PINE_AFALL
PINE_ARISE
PINE_LOW
PINE_HIGH
PINE_FALL
PINE_RISE

*/
hw.SetPinEventDetectMask(buttonPinNumber, govattu.PINE_FALL|govattu.PINE_RISE) //Set event detection flags for specific pin

//And when polling detected events
if hw.ReadPinEvent(buttonPinNumber) {
  //Process event here
	hw.ResetPinEvent(buttonPinNumber) //This is needed for clearing before next readPinEvent
}