go-packages/go-rpio
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Drahoslav 2017-11-20 12:14:52 +01:00
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rpio.go
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@ -1,13 +1,15 @@
/* /*
Package rpio provides GPIO access on the Raspberry PI without any need Package rpio provides GPIO access on the Raspberry PI without any need
for external c libraries (ex: WiringPI or BCM2835). for external c libraries (eg. WiringPi or BCM2835).
Supports simple operations such as: Supports simple operations such as:
- Pin mode/direction (input/output/clock/pwm) - Pin mode/direction (input/output/clock/pwm)
- Pin write (high/low) - Pin write (high/low)
- Pin read (high/low) - Pin read (high/low)
- Pull up/down/off - Pull up/down/off
And clock/pwm related oparations:
- Set Clock frequency
- Set Duty cycle
Example of use: Example of use:
@ -23,36 +25,40 @@ Example of use:
} }
The library use the raw BCM2835 pinouts, not the ports as they are mapped The library use the raw BCM2835 pinouts, not the ports as they are mapped
on the output pins for the raspberry pi on the output pins for the raspberry pi, and not the wiringPi convention.
Rev 1 Raspberry Pi Rev 2 and 3 Raspberry Pi Rev 1 Raspberry Pi (legacy)
+------+------+--------+ +-----+---------+----------+---------+-----+ +-----+--------+----------+--------+-----+
| GPIO | Phys | Name | | BCM | Name | Physical | Name | BCM | | BCM | Name | Physical | Name | BCM |
+------+------+--------+ +-----+---------+----++----+---------+-----+ +-----+--------+----++----+--------+-----+
| 0 | 3 | SDA | | | 3.3v | 1 || 2 | 5v | | | | 3.3v | 1 || 2 | 5v | |
| 1 | 5 | SCL | | 2 | SDA 1 | 3 || 4 | 5v | | | 0 | SDA | 3 || 4 | 5v | |
| 4 | 7 | GPIO 7 | | 3 | SCL 1 | 5 || 6 | 0v | | | 1 | SCL | 5 || 6 | 0v | |
| 7 | 26 | CE1 | | 4 | GPIO 7 | 7 || 8 | TxD | 14 | | 4 | GPIO 7 | 7 || 8 | TxD | 14 |
| 8 | 24 | CE0 | | | 0v | 9 || 10 | RxD | 15 | | | 0v | 9 || 10 | RxD | 15 |
| 9 | 21 | MISO | | 17 | GPIO 0 | 11 || 12 | GPIO 1 | 18 | | 17 | GPIO 0 | 11 || 12 | GPIO 1 | 18 |
| 10 | 19 | MOSI | | 27 | GPIO 2 | 13 || 14 | 0v | | | 21 | GPIO 2 | 13 || 14 | 0v | |
| 11 | 23 | SCLK | | 22 | GPIO 3 | 15 || 16 | GPIO 4 | 23 | | 22 | GPIO 3 | 15 || 16 | GPIO 4 | 23 |
| 14 | 8 | TxD | | | 3.3v | 17 || 18 | GPIO 5 | 24 | | | 3.3v | 17 || 18 | GPIO 5 | 24 |
| 15 | 10 | RxD | | 10 | MOSI | 19 || 20 | 0v | | | 10 | MOSI | 19 || 20 | 0v | |
| 17 | 11 | GPIO 0 | | 9 | MISO | 21 || 22 | GPIO 6 | 25 | | 9 | MISO | 21 || 22 | GPIO 6 | 25 |
| 18 | 12 | GPIO 1 | | 11 | SCLK | 23 || 24 | CE0 | 8 | | 11 | SCLK | 23 || 24 | CE0 | 8 |
| 21 | 13 | GPIO 2 | | | 0v | 25 || 26 | CE1 | 7 | | | 0v | 25 || 26 | CE1 | 7 |
| 22 | 15 | GPIO 3 | | 0 | SDA 0 | 27 || 28 | SCL 0 | 1 | +-----+--------+----++----+--------+-----+
| 23 | 16 | GPIO 4 | | 5 | GPIO 21 | 29 || 30 | 0v | |
| 24 | 18 | GPIO 5 | | 6 | GPIO 22 | 31 || 32 | GPIO 26 | 12 |
| 25 | 22 | GPIO 6 | | 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: See the spec for full details of the BCM2835 controller:
http://www.raspberrypi.org/wp-content/uploads/2012/02/BCM2835-ARM-Peripherals.pdf
https://www.raspberrypi.org/documentation/hardware/raspberrypi/bcm2835/BCM2835-ARM-Peripherals.pdf
and https://elinux.org/BCM2835_datasheet_errata - for errors in that spec
*/ */
package rpio package rpio
import ( import (
@ -208,8 +214,8 @@ func (pin Pin) PullOff() {
// PinMode sets the mode (direction) of a given pin (Input, Output, Clock or Pwm) // 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 // Clock is possible only for pins 4, 5, 6, 20, 21.
// Pwm is possible only for pins 12, 13, 18, 19 // Pwm is possible only for pins 12, 13, 18, 19.
func PinMode(pin Pin, mode Mode) { func PinMode(pin Pin, mode Mode) {
// Pin fsel register, 0 or 1 depending on bank // Pin fsel register, 0 or 1 depending on bank
@ -330,13 +336,16 @@ func PullMode(pin Pin, pull Pull) {
// Set clock speed for given pin in Clock or Pwm mode // Set clock speed for given pin in Clock or Pwm mode
// //
// Param freq should be in range 4688Hz - 19.2MHz to prevent unexpected behavior, // Param freq should be in range 4688Hz - 19.2MHz to prevent unexpected behavior,
// hovewer output frequency of Pwm pins can be further adjusted with setDutyCycle. // however output frequency of Pwm pins can be further adjusted with SetDutyCycle.
// (Thus for smaller frequencies use Pwm pin with large cycle range or implement custom software clock using output pin and sleep.) // 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 // 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 // changing frequency for one pin will change it also for all pins within a group.
// The groups are: clk0 (4, 20, 32, 34), clk1 (5, 21, 42, 43) and clk2 (6 and 43). // The groups are:
// Also all pwm pins (12, 13, 18, 19, 40, 41, 45) share same source clock. // gp_clk0: pins 4, 20, 32, 34
// gp_clk1: pins 5, 21, 42, 43
// gp_clk2: pins 6 and 43
// pwm_clk: pins 12, 13, 18, 19, 40, 41, 45
func SetFreq(pin Pin, freq int) { func SetFreq(pin Pin, freq int) {
// TODO: would be nice to choose best clock source depending on target frequency, oscilator is used for now // TODO: would be nice to choose best clock source depending on target frequency, oscilator is used for now
const sourceFreq = 19200000 // oscilator frequency const sourceFreq = 19200000 // oscilator frequency
@ -398,23 +407,25 @@ func SetFreq(pin Pin, freq int) {
// NOTE without root permission this changes will simply do nothing successfully // NOTE without root permission this changes will simply do nothing successfully
} }
// Set cycle length (range) and duty length (data) for pwm in M/S mode // Set cycle length (range) and duty length (data) for Pwm pin in M/S mode
// //
// |<- duty ->| // |<- duty ->|
// __________ // __________
// _/ \_____________/ // _/ \_____________/
// |<------- cycle -------->| // |<------- cycle -------->|
// //
// Output frequency is computed as pwm clock frequency divided by cycle length // 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: // So, to set Pwm pin to freqency 38kHz with duty cycle 1/4, use this combination:
// //
// pin.Pwm() // pin.Pwm()
// pin.DutyCycle(1, 4) // pin.DutyCycle(1, 4)
// pin.Freq(38000*4) // pin.Freq(38000*4)
// //
// Note that some pins share common pwm channel, // Note that some pins share common pwm channel,
// so calling this function will set same duty cycle for all pins belongig to channel. // so calling this function will set same duty cycle for all pins belonging to channel.
// It is channel 1 (pwm0) for pins 12, 18, 40, and channel 2 (pwm1) for pins 13, 19, 41, 45. // The channels are:
// channel 1 (pwm0) for pins 12, 18, 40
// channel 2 (pwm1) for pins 13, 19, 41, 45.
func SetDutyCycle(pin Pin, dutyLen, cycleLen uint32) { func SetDutyCycle(pin Pin, dutyLen, cycleLen uint32) {
const pwmCtlReg = 0 const pwmCtlReg = 0
var ( var (