README
¶
go-rpio
Native GPIO-Gophers for your Pi!
Documentation: 
go-rpio is a Go library for accessing GPIO-pins on the Raspberry Pi.
It requires no external c libraries such as WiringPI or bcm2835.
There's a tiny bit of additional information over at my blog.
Releases
- 1.0.0 - Supports original rpi A/B/B+
- 2.0.0 - Adds support for rpi 2, by @akramer
- 3.0.0 - Adds support for /dev/gpiomem, by @dotdoom
- 4.0.0 - Adds support for PWM and Clock modes, by @Drahoslav7
- 4.1.0 - Adds support for edge detection, by @Drahoslav7
- 4.2.0 - Faster write and toggle of output pins, by @Drahoslav7
Usage
import "github.com/stianeikeland/go-rpio"
Open memory range for GPIO access in /dev/mem
err := rpio.Open()
Initialize a pin, run basic operations. Pin refers to the bcm2835 pin, not the physical pin on the raspberry pi header. Pin 10 here is exposed on the pin header as physical pin 19.
pin := rpio.Pin(10)
pin.Output() // Output mode
pin.High() // Set pin High
pin.Low() // Set pin Low
pin.Toggle() // Toggle pin (Low -> High -> Low)
pin.Input() // Input mode
res := pin.Read() // Read state from pin (High / Low)
pin.Mode(rpio.Output) // Alternative syntax
pin.Write(rpio.High) // Alternative syntax
Pull up/down/off can be set using:
pin.PullUp()
pin.PullDown()
pin.PullOff()
pin.Pull(rpio.PullUp)
Unmap memory when done
rpio.Close()
Also see example examples/blinker/blinker.go
Other
Currently, it supports basic functionality such as:
- Pin Direction (Input / Output)
- Write (High / Low)
- Read (High / Low)
- Pull (Up / Down / Off)
- PWM (hardware, on supported pins)
- Clock
- Edge detection
It works by memory-mapping the bcm2835 gpio range, and therefore require root/administrative-rights to run.
Using without root
This library can utilize the new /dev/gpiomem memory range if available.
You will probably need to upgrade to the latest kernel (or wait for the next raspbian release) if you're missing /dev/gpiomem. You will also need to add a gpio group, add your user to the group, and then set up udev rules. I would recommend using create_gpio_user_permissions.py if you're unsure how to do this.
PWM modes will still require root.
Documentation
¶
Overview ¶
Package rpio provides GPIO access on the Raspberry PI without any need for external c libraries (eg. WiringPi or BCM2835).
Supports simple operations such as:
- Pin mode/direction (input/output/clock/pwm)
- Pin write (high/low)
- Pin read (high/low)
- Pin edge detection (no/rise/fall/any)
- Pull up/down/off
And clock/pwm related oparations:
- Set Clock frequency
- Set Duty cycle
Example of use:
rpio.Open()
defer rpio.Close()
pin := rpio.Pin(4)
pin.Output()
for {
pin.Toggle()
time.Sleep(time.Second)
}
The library use the raw BCM2835 pinouts, not the ports as they are mapped on the output pins for the raspberry pi, and not the wiringPi convention.
Rev 2 and 3 Raspberry Pi Rev 1 Raspberry Pi (legacy) +-----+---------+----------+---------+-----+ +-----+--------+----------+--------+-----+ | BCM | Name | Physical | Name | BCM | | BCM | Name | Physical | Name | BCM | +-----+---------+----++----+---------+-----+ +-----+--------+----++----+--------+-----+ | | 3.3v | 1 || 2 | 5v | | | | 3.3v | 1 || 2 | 5v | | | 2 | SDA 1 | 3 || 4 | 5v | | | 0 | SDA | 3 || 4 | 5v | | | 3 | SCL 1 | 5 || 6 | 0v | | | 1 | SCL | 5 || 6 | 0v | | | 4 | GPIO 7 | 7 || 8 | TxD | 14 | | 4 | GPIO 7 | 7 || 8 | TxD | 14 | | | 0v | 9 || 10 | RxD | 15 | | | 0v | 9 || 10 | RxD | 15 | | 17 | GPIO 0 | 11 || 12 | GPIO 1 | 18 | | 17 | GPIO 0 | 11 || 12 | GPIO 1 | 18 | | 27 | GPIO 2 | 13 || 14 | 0v | | | 21 | GPIO 2 | 13 || 14 | 0v | | | 22 | GPIO 3 | 15 || 16 | GPIO 4 | 23 | | 22 | GPIO 3 | 15 || 16 | GPIO 4 | 23 | | | 3.3v | 17 || 18 | GPIO 5 | 24 | | | 3.3v | 17 || 18 | GPIO 5 | 24 | | 10 | MOSI | 19 || 20 | 0v | | | 10 | MOSI | 19 || 20 | 0v | | | 9 | MISO | 21 || 22 | GPIO 6 | 25 | | 9 | MISO | 21 || 22 | GPIO 6 | 25 | | 11 | SCLK | 23 || 24 | CE0 | 8 | | 11 | SCLK | 23 || 24 | CE0 | 8 | | | 0v | 25 || 26 | CE1 | 7 | | | 0v | 25 || 26 | CE1 | 7 | | 0 | SDA 0 | 27 || 28 | SCL 0 | 1 | +-----+--------+----++----+--------+-----+ | 5 | GPIO 21 | 29 || 30 | 0v | | | 6 | GPIO 22 | 31 || 32 | GPIO 26 | 12 | | 13 | GPIO 23 | 33 || 34 | 0v | | | 19 | GPIO 24 | 35 || 36 | GPIO 27 | 16 | | 26 | GPIO 25 | 37 || 38 | GPIO 28 | 20 | | | 0v | 39 || 40 | GPIO 29 | 21 | +-----+---------+----++----+---------+-----+
See the spec for full details of the BCM2835 controller:
https://www.raspberrypi.org/documentation/hardware/raspberrypi/bcm2835/BCM2835-ARM-Peripherals.pdf and https://elinux.org/BCM2835_datasheet_errata - for errors in that spec
Index ¶
- func Close() error
- func DetectEdge(pin Pin, edge Edge)
- func EdgeDetected(pin Pin) bool
- func Open() (err error)
- func PinMode(pin Pin, mode Mode)
- func PullMode(pin Pin, pull Pull)
- func SetDutyCycle(pin Pin, dutyLen, cycleLen uint32)
- func SetFreq(pin Pin, freq int)
- func StartPwm()
- func StopPwm()
- func TogglePin(pin Pin)
- func WritePin(pin Pin, state State)
- type Edge
- type Mode
- type Pin
- func (pin Pin) Clock()
- func (pin Pin) Detect(edge Edge)
- func (pin Pin) DutyCycle(dutyLen, cycleLen uint32)
- func (pin Pin) EdgeDetected() bool
- func (pin Pin) Freq(freq int)
- func (pin Pin) High()
- func (pin Pin) Input()
- func (pin Pin) Low()
- func (pin Pin) Mode(mode Mode)
- func (pin Pin) Output()
- func (pin Pin) Pull(pull Pull)
- func (pin Pin) PullDown()
- func (pin Pin) PullOff()
- func (pin Pin) PullUp()
- func (pin Pin) Pwm()
- func (pin Pin) Read() State
- func (pin Pin) Toggle()
- func (pin Pin) Write(state State)
- type Pull
- type State
Constants ¶
This section is empty.
Variables ¶
This section is empty.
Functions ¶
func DetectEdge ¶
Enable edge event detection on pin.
Combine with pin.EdgeDetected() to check whether event occured.
Note that using this function might conflict with the same functionality of other gpio library.
It also clears previously detected event of this pin if any.
Note that call with RiseEdge will disable previously set FallEdge detection and vice versa. You have to call with AnyEdge, to enable detection for both edges. To disable previously enabled detection call it with NoEdge.
func EdgeDetected ¶
Check whether edge event occured since last call or since detection was enabled
There is no way (yet) to handle interruption caused by edge event, you have to use polling.
Event detection has to be enabled first, by pin.Detect(edge)
func Open ¶
func Open() (err error)
Open and memory map GPIO memory range from /dev/mem . Some reflection magic is used to convert it to a unsafe []uint32 pointer
func PinMode ¶
PinMode sets the mode (direction) of a given pin (Input, Output, Clock or Pwm)
Clock is possible only for pins 4, 5, 6, 20, 21. Pwm is possible only for pins 12, 13, 18, 19.
func SetDutyCycle ¶
Set cycle length (range) and duty length (data) for Pwm pin in M/S mode
|<- duty ->| __________ _/ \_____________/ |<------- cycle -------->|
Output frequency is computed as pwm clock frequency divided by cycle length. So, to set Pwm pin to freqency 38kHz with duty cycle 1/4, use this combination:
pin.Pwm() pin.DutyCycle(1, 4) pin.Freq(38000*4)
Note that some pins share common pwm channel, so calling this function will set same duty cycle for all pins belonging to channel. The channels are:
channel 1 (pwm0) for pins 12, 18, 40 channel 2 (pwm1) for pins 13, 19, 41, 45.
func SetFreq ¶
Set clock speed for given pin in Clock or Pwm mode
Param freq should be in range 4688Hz - 19.2MHz to prevent unexpected behavior, however output frequency of Pwm pins can be further adjusted with SetDutyCycle. So for smaller frequencies use Pwm pin with large cycle range. (Or implement custom software clock using output pin and sleep.)
Note that some pins share the same clock source, it means that changing frequency for one pin will change it also for all pins within a group. The groups are:
gp_clk0: pins 4, 20, 32, 34 gp_clk1: pins 5, 21, 42, 44 gp_clk2: pins 6 and 43 pwm_clk: pins 12, 13, 18, 19, 40, 41, 45
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