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Update doc overview
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Drahoslav
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rpio.go
89
rpio.go
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@ -1,13 +1,15 @@
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/*
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Package rpio provides GPIO access on the Raspberry PI without any need
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for external c libraries (ex: WiringPI or BCM2835).
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for external c libraries (eg. WiringPi or BCM2835).
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Supports simple operations such as:
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- Pin mode/direction (input/output/clock/pwm)
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- Pin write (high/low)
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- Pin read (high/low)
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- Pull up/down/off
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And clock/pwm related oparations:
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- Set Clock frequency
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- Set Duty cycle
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Example of use:
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@ -23,36 +25,40 @@ Example of use:
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}
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The library use the raw BCM2835 pinouts, not the ports as they are mapped
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on the output pins for the raspberry pi
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on the output pins for the raspberry pi, and not the wiringPi convention.
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Rev 1 Raspberry Pi
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+------+------+--------+
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| GPIO | Phys | Name |
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+------+------+--------+
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| 0 | 3 | SDA |
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| 1 | 5 | SCL |
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| 4 | 7 | GPIO 7 |
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| 7 | 26 | CE1 |
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| 8 | 24 | CE0 |
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| 9 | 21 | MISO |
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| 10 | 19 | MOSI |
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| 11 | 23 | SCLK |
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| 14 | 8 | TxD |
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| 15 | 10 | RxD |
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| 17 | 11 | GPIO 0 |
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| 18 | 12 | GPIO 1 |
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| 21 | 13 | GPIO 2 |
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| 22 | 15 | GPIO 3 |
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| 23 | 16 | GPIO 4 |
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| 24 | 18 | GPIO 5 |
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| 25 | 22 | GPIO 6 |
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+------+------+--------+
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Rev 2 and 3 Raspberry Pi Rev 1 Raspberry Pi (legacy)
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+-----+---------+----------+---------+-----+ +-----+--------+----------+--------+-----+
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| BCM | Name | Physical | Name | BCM | | BCM | Name | Physical | Name | BCM |
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+-----+---------+----++----+---------+-----+ +-----+--------+----++----+--------+-----+
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| | 3.3v | 1 || 2 | 5v | | | | 3.3v | 1 || 2 | 5v | |
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| 2 | SDA 1 | 3 || 4 | 5v | | | 0 | SDA | 3 || 4 | 5v | |
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| 3 | SCL 1 | 5 || 6 | 0v | | | 1 | SCL | 5 || 6 | 0v | |
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| 4 | GPIO 7 | 7 || 8 | TxD | 14 | | 4 | GPIO 7 | 7 || 8 | TxD | 14 |
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| | 0v | 9 || 10 | RxD | 15 | | | 0v | 9 || 10 | RxD | 15 |
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| 17 | GPIO 0 | 11 || 12 | GPIO 1 | 18 | | 17 | GPIO 0 | 11 || 12 | GPIO 1 | 18 |
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| 27 | GPIO 2 | 13 || 14 | 0v | | | 21 | GPIO 2 | 13 || 14 | 0v | |
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| 22 | GPIO 3 | 15 || 16 | GPIO 4 | 23 | | 22 | GPIO 3 | 15 || 16 | GPIO 4 | 23 |
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| | 3.3v | 17 || 18 | GPIO 5 | 24 | | | 3.3v | 17 || 18 | GPIO 5 | 24 |
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| 10 | MOSI | 19 || 20 | 0v | | | 10 | MOSI | 19 || 20 | 0v | |
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| 9 | MISO | 21 || 22 | GPIO 6 | 25 | | 9 | MISO | 21 || 22 | GPIO 6 | 25 |
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| 11 | SCLK | 23 || 24 | CE0 | 8 | | 11 | SCLK | 23 || 24 | CE0 | 8 |
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| | 0v | 25 || 26 | CE1 | 7 | | | 0v | 25 || 26 | CE1 | 7 |
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| 0 | SDA 0 | 27 || 28 | SCL 0 | 1 | +-----+--------+----++----+--------+-----+
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| 5 | GPIO 21 | 29 || 30 | 0v | |
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| 6 | GPIO 22 | 31 || 32 | GPIO 26 | 12 |
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| 13 | GPIO 23 | 33 || 34 | 0v | |
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| 19 | GPIO 24 | 35 || 36 | GPIO 27 | 16 |
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| 26 | GPIO 25 | 37 || 38 | GPIO 28 | 20 |
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| | 0v | 39 || 40 | GPIO 29 | 21 |
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+-----+---------+----++----+---------+-----+
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See the spec for full details of the BCM2835 controller:
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http://www.raspberrypi.org/wp-content/uploads/2012/02/BCM2835-ARM-Peripherals.pdf
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https://www.raspberrypi.org/documentation/hardware/raspberrypi/bcm2835/BCM2835-ARM-Peripherals.pdf
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and https://elinux.org/BCM2835_datasheet_errata - for errors in that spec
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*/
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package rpio
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import (
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@ -208,8 +214,8 @@ func (pin Pin) PullOff() {
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// PinMode sets the mode (direction) of a given pin (Input, Output, Clock or Pwm)
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//
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// Clock is possible only for pins 4, 5, 6, 20, 21
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// Pwm is possible only for pins 12, 13, 18, 19
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// Clock is possible only for pins 4, 5, 6, 20, 21.
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// Pwm is possible only for pins 12, 13, 18, 19.
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func PinMode(pin Pin, mode Mode) {
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// Pin fsel register, 0 or 1 depending on bank
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@ -330,13 +336,16 @@ func PullMode(pin Pin, pull Pull) {
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// Set clock speed for given pin in Clock or Pwm mode
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//
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// Param freq should be in range 4688Hz - 19.2MHz to prevent unexpected behavior,
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// hovewer output frequency of Pwm pins can be further adjusted with setDutyCycle.
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// (Thus for smaller frequencies use Pwm pin with large cycle range or implement custom software clock using output pin and sleep.)
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// however output frequency of Pwm pins can be further adjusted with SetDutyCycle.
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// So for smaller frequencies use Pwm pin with large cycle range. (Or implement custom software clock using output pin and sleep.)
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//
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// Note that some pins share the same clock source, it means that
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// changing frequency for one pin will change it also for all pins within a group
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// The groups are: clk0 (4, 20, 32, 34), clk1 (5, 21, 42, 43) and clk2 (6 and 43).
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// Also all pwm pins (12, 13, 18, 19, 40, 41, 45) share same source clock.
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// changing frequency for one pin will change it also for all pins within a group.
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// The groups are:
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// gp_clk0: pins 4, 20, 32, 34
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// gp_clk1: pins 5, 21, 42, 43
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// gp_clk2: pins 6 and 43
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// pwm_clk: pins 12, 13, 18, 19, 40, 41, 45
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func SetFreq(pin Pin, freq int) {
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// TODO: would be nice to choose best clock source depending on target frequency, oscilator is used for now
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const sourceFreq = 19200000 // oscilator frequency
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@ -398,23 +407,25 @@ func SetFreq(pin Pin, freq int) {
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// NOTE without root permission this changes will simply do nothing successfully
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}
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// Set cycle length (range) and duty length (data) for pwm in M/S mode
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// Set cycle length (range) and duty length (data) for Pwm pin in M/S mode
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//
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// |<- duty ->|
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// __________
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// _/ \_____________/
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// |<------- cycle -------->|
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//
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// Output frequency is computed as pwm clock frequency divided by cycle length
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// So, to set Pwm pin to freqency 38kHz with duty cycle 1/4 use this combination:
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// Output frequency is computed as pwm clock frequency divided by cycle length.
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// So, to set Pwm pin to freqency 38kHz with duty cycle 1/4, use this combination:
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//
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// pin.Pwm()
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// pin.DutyCycle(1, 4)
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// pin.Freq(38000*4)
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//
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// Note that some pins share common pwm channel,
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// so calling this function will set same duty cycle for all pins belongig to channel.
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// It is channel 1 (pwm0) for pins 12, 18, 40, and channel 2 (pwm1) for pins 13, 19, 41, 45.
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// so calling this function will set same duty cycle for all pins belonging to channel.
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// The channels are:
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// channel 1 (pwm0) for pins 12, 18, 40
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// channel 2 (pwm1) for pins 13, 19, 41, 45.
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func SetDutyCycle(pin Pin, dutyLen, cycleLen uint32) {
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const pwmCtlReg = 0
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var (
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