Apple2-IO-RPi/RaspberryPi/apple2driver/a2io/gpio.go

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// Copyright Terence J. Boldt (c)2020-2021
// Use of this source code is governed by an MIT
// license that can be found in the LICENSE file.
// This file is used for communicating with the Apple II data bus via the
// GPIO ports on the Raspberry Pi
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package a2io
import (
"bytes"
"errors"
"fmt"
"time"
"periph.io/x/periph/conn/gpio"
"periph.io/x/periph/conn/gpio/gpioreg"
"periph.io/x/periph/host"
)
var edgeTimeout time.Duration
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var outWrite gpio.PinIO
var outRead gpio.PinIO
var outReserved2 gpio.PinIO
var outReserved1 gpio.PinIO
var outBit7 gpio.PinIO
var outBit6 gpio.PinIO
var outBit5 gpio.PinIO
var outBit4 gpio.PinIO
var outBit3 gpio.PinIO
var outBit2 gpio.PinIO
var outBit1 gpio.PinIO
var outBit0 gpio.PinIO
var inWrite gpio.PinIO
var inRead gpio.PinIO
var inReserved2 gpio.PinIO
var inReserved1 gpio.PinIO
var inBit7 gpio.PinIO
var inBit6 gpio.PinIO
var inBit5 gpio.PinIO
var inBit4 gpio.PinIO
var inBit3 gpio.PinIO
var inBit2 gpio.PinIO
var inBit1 gpio.PinIO
var inBit0 gpio.PinIO
// A2Gpio is the live implementation of A2Io interface
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type A2Gpio struct {
}
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// Init initializes the GPIO ports on the Raspberry Pi
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func (a2 A2Gpio) Init() {
host.Init()
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outWrite = gpioreg.ByName("GPIO24")
outRead = gpioreg.ByName("GPIO25")
outReserved2 = gpioreg.ByName("GPIO7") //note GPIO7 and CPIO8 require extra effort to use
outReserved1 = gpioreg.ByName("GPIO8")
outBit7 = gpioreg.ByName("GPIO5")
outBit6 = gpioreg.ByName("GPIO11")
outBit5 = gpioreg.ByName("GPIO9")
outBit4 = gpioreg.ByName("GPIO10")
outBit3 = gpioreg.ByName("GPIO22")
outBit2 = gpioreg.ByName("GPIO27")
outBit1 = gpioreg.ByName("GPIO17")
outBit0 = gpioreg.ByName("GPIO4")
inWrite = gpioreg.ByName("GPIO23")
inRead = gpioreg.ByName("GPIO18")
inReserved2 = gpioreg.ByName("GPIO14")
inReserved1 = gpioreg.ByName("GPIO15")
inBit7 = gpioreg.ByName("GPIO12")
inBit6 = gpioreg.ByName("GPIO16")
inBit5 = gpioreg.ByName("GPIO20")
inBit4 = gpioreg.ByName("GPIO21")
inBit3 = gpioreg.ByName("GPIO26")
inBit2 = gpioreg.ByName("GPIO19")
inBit1 = gpioreg.ByName("GPIO13")
inBit0 = gpioreg.ByName("GPIO6")
inWrite.In(gpio.PullDown, gpio.BothEdges)
inRead.In(gpio.PullDown, gpio.BothEdges)
outReserved1.Out(gpio.High)
outReserved2.Out(gpio.High)
outRead.Out(gpio.High)
outWrite.Out(gpio.High)
outBit7.Out(gpio.Low)
outBit6.Out(gpio.Low)
outBit5.Out(gpio.Low)
outBit4.Out(gpio.Low)
outBit3.Out(gpio.Low)
outBit2.Out(gpio.Low)
outBit1.Out(gpio.Low)
outBit0.Out(gpio.Low)
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edgeTimeout = time.Second
}
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// ReadString reads a string from the Apple II via Raspberry Pi's GPIO ports
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func (a2 A2Gpio) ReadString() (string, error) {
var inBytes bytes.Buffer
for {
inByte, err := a2.ReadByte()
if err != nil {
return "", err
}
if inByte == 0 {
break
}
inBytes.WriteByte(inByte)
}
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return inBytes.String(), nil
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}
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// WriteString writes a string to the Apple II via Raspberry Pi's GPIO ports
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func (a2 A2Gpio) WriteString(outString string) error {
for _, character := range outString {
err := a2.WriteByte(byte(character) | 128)
if err != nil {
fmt.Printf("Failed to write string\n")
return err
}
}
a2.WriteByte(0)
return nil
}
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// ReadByte reads a byte from the Apple II via Raspberry Pi's GPIO ports
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func (a2 A2Gpio) ReadByte() (byte, error) {
// let the Apple II know we are ready to read
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outRead.Out(gpio.Low)
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// wait for the Apple II to write
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for inWrite.Read() == gpio.High {
if !inWrite.WaitForEdge(edgeTimeout) {
outRead.Out(gpio.High)
return 0, errors.New("timed out reading byte -- write stuck high")
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}
}
// get a nibble of data
var data byte
data = 0
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bit7 := inBit7.Read()
bit6 := inBit6.Read()
bit5 := inBit5.Read()
bit4 := inBit4.Read()
bit3 := inBit3.Read()
bit2 := inBit2.Read()
bit1 := inBit1.Read()
bit0 := inBit0.Read()
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if bit7 == gpio.High {
data += 128
}
if bit6 == gpio.High {
data += 64
}
if bit5 == gpio.High {
data += 32
}
if bit4 == gpio.High {
data += 16
}
if bit3 == gpio.High {
data += 8
}
if bit2 == gpio.High {
data += 4
}
if bit1 == gpio.High {
data += 2
}
if bit0 == gpio.High {
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data++
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}
// let the Apple II know we are done reading
//fmt.Printf("let the Apple II know we are done reading\n")
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outRead.Out(gpio.High)
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// wait for the Apple II to finish writing
//fmt.Printf("wait for the Apple II to finish writing\n")
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for inWrite.Read() == gpio.Low {
if !inWrite.WaitForEdge(edgeTimeout) {
return 0, errors.New("timed out reading byte -- write stuck low")
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}
}
return data, nil
}
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// WriteByte writes a byte to the Apple II via Raspberry Pi's GPIO ports
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func (a2 A2Gpio) WriteByte(data byte) error {
// check if the Apple II wants to send a byte to us first
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if inWrite.Read() == gpio.Low {
outWrite.Out(gpio.High)
return errors.New("can't write byte while byte is incoming")
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}
// wait for the Apple II to be ready to read
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for inRead.Read() == gpio.High {
if !inRead.WaitForEdge(edgeTimeout) {
outWrite.Out(gpio.High)
return errors.New("timed out writing byte -- read stuck high")
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}
}
bit7 := gpio.Low
bit6 := gpio.Low
bit5 := gpio.Low
bit4 := gpio.Low
bit3 := gpio.Low
bit2 := gpio.Low
bit1 := gpio.Low
bit0 := gpio.Low
if ((data & 128) >> 7) == 1 {
bit7 = gpio.High
}
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outBit7.Out(bit7)
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if ((data & 64) >> 6) == 1 {
bit6 = gpio.High
}
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outBit6.Out(bit6)
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if ((data & 32) >> 5) == 1 {
bit5 = gpio.High
}
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outBit5.Out(bit5)
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if ((data & 16) >> 4) == 1 {
bit4 = gpio.High
}
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outBit4.Out(bit4)
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if ((data & 8) >> 3) == 1 {
bit3 = gpio.High
}
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outBit3.Out(bit3)
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if ((data & 4) >> 2) == 1 {
bit2 = gpio.High
}
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outBit2.Out(bit2)
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if ((data & 2) >> 1) == 1 {
bit1 = gpio.High
}
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outBit1.Out(bit1)
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if (data & 1) == 1 {
bit0 = gpio.High
}
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outBit0.Out(bit0)
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// let Apple II know we're writing
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outWrite.Out(gpio.Low)
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// wait for the Apple II to finsih reading
//fmt.Printf("wait for the Apple II to finsih reading\n")
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for inRead.Read() == gpio.Low {
if !inRead.WaitForEdge(edgeTimeout) {
outWrite.Out(gpio.High)
return errors.New("timed out writing byte -- read stuck low")
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}
}
// let the Apple II know we are done writing
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outWrite.Out(gpio.High)
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return nil
}
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// WriteBlock writes 512 bytes to the Apple II via Raspberry Pi's GPIO ports
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func (a2 A2Gpio) WriteBlock(buffer []byte) error {
for i := 0; i < 512; i++ {
err := a2.WriteByte(buffer[i])
if err != nil {
return err
}
}
return nil
}
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// ReadBlock reads 512 bytes from the Apple II via Raspberry Pi's GPIO ports
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func (a2 A2Gpio) ReadBlock(buffer []byte) error {
var err error
for i := 0; i < 512; i++ {
buffer[i], err = a2.ReadByte()
if err != nil {
return err
}
}
return nil
}
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// WriteBuffer writes a buffer of bytes to the Apple II via Raspberry Pi's GPIO ports
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func (a2 A2Gpio) WriteBuffer(buffer []byte) error {
bufferSize := len(buffer)
for i := 0; i < bufferSize; i++ {
err := a2.WriteByte(buffer[i])
if err != nil {
return err
}
}
return nil
}