diff --git a/go.mod b/go.mod index da5784d..b49f549 100644 --- a/go.mod +++ b/go.mod @@ -1 +1,3 @@ module github.com/stianeikeland/go-rpio/v4 + +go 1.13 diff --git a/rpio.go b/rpio.go index 13157c1..44851ab 100644 --- a/rpio.go +++ b/rpio.go @@ -63,6 +63,8 @@ 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 +Changes to support the BCM2711, used on the Raspberry Pi 4, were cribbed from https://github.com/RPi-Distro/raspi-gpio/ + */ package rpio @@ -96,6 +98,14 @@ const ( memLength = 4096 ) +// BCM 2711 has a differnet mechanism for pin pull-up/pull-down/enable +const ( + GPPUPPDN0 = 57 // Pin pull-up/down for pins 15:0 + GPPUPPDN1 = 58 // Pin pull-up/down for pins 31:16 + GPPUPPDN2 = 59 // Pin pull-up/down for pins 47:32 + GPPUPPDN3 = 60 // Pin pull-up/down for pins 57:48 +) + var ( gpioBase int64 clkBase int64 @@ -240,6 +250,25 @@ func (pin Pin) PullOff() { PullMode(pin, PullOff) } +func (pin Pin) ReadPull() Pull { + if !isBCM2711() { + return PullOff // TODO: Can you read pull state on other Pi boards? + } + + reg := GPPUPPDN0 + (uint8(pin) >> 4) + bits := gpioMem[reg] >> ((uint8(pin) & 0xf) << 1) & 0x3 + switch bits { + case 0: + return PullOff + case 1: + return PullUp + case 2: + return PullDown + default: + return PullOff + } +} + // Detect: Enable edge event detection on pin func (pin Pin) Detect(edge Edge) { DetectEdge(pin, edge) @@ -430,32 +459,54 @@ func EdgeDetected(pin Pin) bool { } func PullMode(pin Pin, pull Pull) { - // Pull up/down/off register has offset 38 / 39, pull is 37 - pullClkReg := pin/32 + 38 - pullReg := 37 - shift := pin % 32 - + memlock.Lock() defer memlock.Unlock() - switch pull { - case PullDown, PullUp: - gpioMem[pullReg] |= uint32(pull) - case PullOff: + if isBCM2711() { + pullreg := GPPUPPDN0 + (pin >> 4) + pullshift := (pin & 0xf) << 1 + + var p uint32 + + switch pull { + case PullOff: + p = 0 + case PullUp: + p = 1 + case PullDown: + p = 2; + } + + // This is verbatim C code from raspi-gpio.c + pullbits := gpioMem[pullreg] + pullbits &= ^(3 << pullshift) + pullbits |= (p << pullshift) + gpioMem[pullreg]= pullbits + } else { + // Pull up/down/off register has offset 38 / 39, pull is 37 + pullClkReg := pin/32 + 38 + pullReg := 37 + shift := pin % 32 + + switch pull { + case PullDown, PullUp: + gpioMem[pullReg] |= uint32(pull) + case PullOff: + gpioMem[pullReg] &^= 3 + } + + // Wait for value to clock in, this is ugly, sorry :( + time.Sleep(time.Microsecond) + + gpioMem[pullClkReg] = 1 << shift + + // Wait for value to clock in + time.Sleep(time.Microsecond) + gpioMem[pullReg] &^= 3 + gpioMem[pullClkReg] = 0 } - - // Wait for value to clock in, this is ugly, sorry :( - time.Sleep(time.Microsecond) - - gpioMem[pullClkReg] = 1 << shift - - // Wait for value to clock in - time.Sleep(time.Microsecond) - - gpioMem[pullReg] &^= 3 - gpioMem[pullClkReg] = 0 - } // SetFreq: Set clock speed for given pin in Clock or Pwm mode @@ -755,3 +806,9 @@ func getBase() int64 { // Default to Pi 1 return int64(bcm2835Base) } + +// The Pi 4 uses a BCM 2711, which has different register offsets and base addresses than the rest of the Pi family (so far). This +// helper function checks if we're on a 2711 and hence a Pi 4 +func isBCM2711() bool { + return gpioMem[GPPUPPDN3] != 0x6770696f +}