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|
//go:build mimxrt1062
package machine
import (
"device/nxp"
"runtime/interrupt"
"runtime/volatile"
)
// UART peripheral abstraction layer for the MIMXRT1062
type UART struct {
Bus *nxp.LPUART_Type
Buffer *RingBuffer
Interrupt interrupt.Interrupt
// txBuffer should be allocated globally (such as when UART is created) to
// prevent it being reclaimed or cleaned up prematurely.
txBuffer *RingBuffer
// these hold the input selector ("daisy chain") values that select which pins
// are connected to the LPUART device, and should be defined where the UART
// instance is declared. see the godoc comments on type muxSelect for more
// details.
muxRX, muxTX muxSelect
// these are copied from UARTConfig, during (*UART).Configure(UARTConfig), and
// should be considered read-only for internal reference (i.e., modifying them
// will have no desirable effect).
rx, tx Pin
baud uint32
// auxiliary state data used internally
configured bool
transmitting volatile.Register32
}
func (uart *UART) isTransmitting() bool { return uart.transmitting.Get() != 0 }
func (uart *UART) startTransmitting() { uart.transmitting.Set(1) }
func (uart *UART) stopTransmitting() { uart.transmitting.Set(0) }
func (uart *UART) resetTransmitting() {
uart.stopTransmitting()
uart.Bus.GLOBAL.SetBits(nxp.LPUART_GLOBAL_RST)
uart.Bus.GLOBAL.ClearBits(nxp.LPUART_GLOBAL_RST)
}
// Configure initializes a UART with the given UARTConfig and other default
// settings.
func (uart *UART) Configure(config UARTConfig) {
const defaultUartFreq = 115200
// use default baud rate if not specified
if config.BaudRate == 0 {
config.BaudRate = defaultUartFreq
}
// use default UART pins if not specified
if config.RX == 0 && config.TX == 0 {
config.RX = UART_RX_PIN
config.TX = UART_TX_PIN
}
uart.baud = config.BaudRate
uart.rx = config.RX
uart.tx = config.TX
// configure the mux and pad control registers
uart.rx.Configure(PinConfig{Mode: PinModeUARTRX})
uart.tx.Configure(PinConfig{Mode: PinModeUARTTX})
// configure the mux input selector
uart.muxRX.connect()
uart.muxTX.connect()
// reset all internal logic and registers
uart.resetTransmitting()
// disable until we have finished configuring registers
uart.Bus.CTRL.Set(0)
// determine the baud rate and over-sample divisors
sbr, osr := uart.getBaudRateDivisor(uart.baud)
// set the baud rate, over-sample configuration, stop bits
baudBits := (((osr - 1) << nxp.LPUART_BAUD_OSR_Pos) & nxp.LPUART_BAUD_OSR_Msk) |
((sbr << nxp.LPUART_BAUD_SBR_Pos) & nxp.LPUART_BAUD_SBR_Msk)
if osr <= 8 {
// if OSR less than or equal to 8, we must enable sampling on both edges
baudBits |= nxp.LPUART_BAUD_BOTHEDGE
}
uart.Bus.BAUD.Set(baudBits)
uart.Bus.PINCFG.Set(0) // disable triggers
// configure watermarks, flush and enable TX/RX FIFOs
rxSize, txSize := uart.getFIFOSize()
rxWater := rxSize >> 1
if rxWater > uint32(nxp.LPUART_FIFO_RXFIFOSIZE_Msk>>nxp.LPUART_FIFO_RXFIFOSIZE_Pos) {
rxWater = uint32(nxp.LPUART_FIFO_RXFIFOSIZE_Msk >> nxp.LPUART_FIFO_RXFIFOSIZE_Pos)
}
txWater := txSize >> 1
if txWater > uint32(nxp.LPUART_FIFO_TXFIFOSIZE_Msk>>nxp.LPUART_FIFO_TXFIFOSIZE_Pos) {
txWater = uint32(nxp.LPUART_FIFO_TXFIFOSIZE_Msk >> nxp.LPUART_FIFO_TXFIFOSIZE_Pos)
}
uart.Bus.WATER.Set(
((rxWater << nxp.LPUART_WATER_RXWATER_Pos) & nxp.LPUART_WATER_RXWATER_Msk) |
((txWater << nxp.LPUART_WATER_TXWATER_Pos) & nxp.LPUART_WATER_TXWATER_Msk))
uart.Bus.FIFO.SetBits(nxp.LPUART_FIFO_RXFE | nxp.LPUART_FIFO_TXFE |
nxp.LPUART_FIFO_RXFLUSH | nxp.LPUART_FIFO_TXFLUSH)
// for now we assume some configuration. in particular:
// Data bits -> 8-bit
// Parity bit -> None (parity bit generation disabled)
// Stop bits -> 1 stop bit
// MSB first -> false
// RX idle type -> idle count starts after start bit
// RX idle config -> 1 idle character
// RX RTS enabled -> false
// TX CTS enabled -> false
// enable transmitter, receiver functions
uart.Bus.CTRL.Set(nxp.LPUART_CTRL_TE | nxp.LPUART_CTRL_RE |
// enable receiver, idle line interrupts
nxp.LPUART_CTRL_RIE | nxp.LPUART_CTRL_ILIE)
// clear all status flags
uart.Bus.STAT.Set(uart.Bus.STAT.Get())
// enable RX interrupt
uart.Interrupt.SetPriority(0xC0)
uart.Interrupt.Enable()
uart.configured = true
}
// Disable disables the UART interface.
//
// If any buffered data has not yet been transmitted, Disable waits until
// transmission completes before disabling the interface. The receiver UART's
// interrupt is also disabled, and the RX/TX pins are reconfigured for GPIO
// input (pull-up).
func (uart *UART) Disable() {
// first ensure the device is enabled
if uart.configured {
// wait for any buffered data to send
uart.Sync()
// stop trapping RX interrupts
uart.Interrupt.Disable()
// reset all internal registers
uart.resetTransmitting()
// disable RX/TX functions
uart.Bus.CTRL.ClearBits(nxp.LPUART_CTRL_TE | nxp.LPUART_CTRL_RE)
// put pins back into GPIO mode
uart.rx.Configure(PinConfig{Mode: PinInputPullup})
uart.tx.Configure(PinConfig{Mode: PinInputPullup})
}
uart.configured = false
}
// Sync blocks the calling goroutine until all data in the output buffer has
// been transmitted.
func (uart *UART) Sync() error {
for uart.isTransmitting() {
}
return nil
}
// WriteByte writes a single byte of data to the UART interface.
func (uart *UART) writeByte(c byte) error {
uart.startTransmitting()
for !uart.txBuffer.Put(c) {
}
uart.Bus.CTRL.SetBits(nxp.LPUART_CTRL_TIE)
return nil
}
func (uart *UART) flush() {}
// getBaudRateDivisor finds the greatest over-sampling factor (4..32) and
// corresponding baud rate divisor (1..8191) that best partition a given baud
// rate into equal intervals.
//
// This is an integral (non-floating point) translation of the logic at the
// beginning of:
//
// void HardwareSerial::begin(uint32_t baud, uint16_t format)
//
// (from Teensyduino: cores/teensy4/HardwareSerial.cpp)
//
// We don't want to use floating point here in case it gets called from an ISR
// or very early during system init.
func (uart *UART) getBaudRateDivisor(baudRate uint32) (sbr uint32, osr uint32) {
const clock = 24000000 // UART is muxed to 24 MHz OSC
err := uint32(0xFFFFFFFF)
sbr, osr = 0, 0
for o := uint32(4); o <= 32; o++ {
s := ((clock*10)/(baudRate*o) + 5) / 10
if s == 0 {
s = 1
}
b := clock / (s * o)
var e uint32
if b > baudRate {
e = b - baudRate
} else {
e = baudRate - b
}
if e <= err {
err = e
osr = o
sbr = s
}
}
return sbr, osr
}
func (uart *UART) getFIFOSize() (rx, tx uint32) {
fifo := uart.Bus.FIFO.Get()
rx = uint32(1) << ((fifo & nxp.LPUART_FIFO_RXFIFOSIZE_Msk) >> nxp.LPUART_FIFO_RXFIFOSIZE_Pos)
if rx > 1 {
rx <<= 1
}
tx = uint32(1) << ((fifo & nxp.LPUART_FIFO_TXFIFOSIZE_Msk) >> nxp.LPUART_FIFO_TXFIFOSIZE_Pos)
if tx > 1 {
tx <<= 1
}
return rx, tx
}
func (uart *UART) getStatus() uint32 {
return uart.Bus.STAT.Get() |
((uart.Bus.FIFO.Get() & uint32(nxp.LPUART_FIFO_TXEMPT_Msk|nxp.LPUART_FIFO_RXEMPT_Msk|
nxp.LPUART_FIFO_TXOF_Msk|nxp.LPUART_FIFO_RXUF_Msk)) >> 16)
}
func (uart *UART) getEnabledInterrupts() uint32 {
return ((uart.Bus.BAUD.Get() & uint32(nxp.LPUART_BAUD_LBKDIE_Msk|nxp.LPUART_BAUD_RXEDGIE_Msk)) >> 8) |
((uart.Bus.FIFO.Get() & uint32(nxp.LPUART_FIFO_TXOFE_Msk|nxp.LPUART_FIFO_RXUFE_Msk)) >> 8) |
(uart.Bus.CTRL.Get() & uint32(0xFF0C000))
}
func (uart *UART) disableInterrupts(mask uint32) {
uart.Bus.BAUD.ClearBits((mask << 8) & uint32(nxp.LPUART_BAUD_LBKDIE_Msk|nxp.LPUART_BAUD_RXEDGIE_Msk))
uart.Bus.FIFO.Set((uart.Bus.FIFO.Get() & ^uint32(nxp.LPUART_FIFO_TXOF_Msk|nxp.LPUART_FIFO_RXUF_Msk)) &
^uint32((mask<<8)&(nxp.LPUART_FIFO_TXOFE_Msk|nxp.LPUART_FIFO_RXUFE_Msk)))
mask &= uint32(0xFFFFFF00)
uart.Bus.CTRL.ClearBits(mask)
}
func (uart *UART) handleInterrupt(interrupt.Interrupt) {
stat := uart.getStatus()
inte := uart.getEnabledInterrupts()
_, txSize := uart.getFIFOSize()
// check for and clear overrun, otherwise RX will not work
if (stat & uint32(nxp.LPUART_STAT_OR)) != 0 {
uart.Bus.STAT.Set((uart.Bus.STAT.Get() & uint32(0x3FE00000)) | nxp.LPUART_STAT_OR)
}
// idle or receive data register is full
if (stat & uint32(nxp.LPUART_STAT_RDRF|nxp.LPUART_STAT_IDLE)) != 0 {
count := (uart.Bus.WATER.Get() & uint32(nxp.LPUART_WATER_RXCOUNT_Msk)) >> nxp.LPUART_WATER_RXCOUNT_Pos
for ; count > 0; count-- {
// read up to 8 bits of data at a time
// TODO: 7, 9, and 10-bit support?
uart.Buffer.Put(uint8(uart.Bus.DATA.Get() & uint32(0xFF)))
}
// if it was an IDLE status, clear the flag
if (stat & uint32(nxp.LPUART_STAT_IDLE)) != 0 {
uart.Bus.STAT.SetBits(nxp.LPUART_STAT_IDLE)
}
// disable idle line interrupts
uart.disableInterrupts(nxp.LPUART_CTRL_RIE | nxp.LPUART_CTRL_ORIE)
}
// check if we have data to write
if ((inte & nxp.LPUART_CTRL_TIE) != 0) && ((stat & nxp.LPUART_STAT_TDRE) != 0) {
for ((uart.Bus.WATER.Get() & uint32(nxp.LPUART_WATER_TXCOUNT_Msk)) >> nxp.LPUART_WATER_TXCOUNT_Pos) < txSize {
if b, ok := uart.txBuffer.Get(); ok {
uart.Bus.DATA.Set(uint32(b))
} else {
break
}
}
if uart.Bus.STAT.HasBits(nxp.LPUART_STAT_TDRE) {
uart.Bus.CTRL.Set((uart.Bus.CTRL.Get() & ^uint32(nxp.LPUART_CTRL_TIE)) | nxp.LPUART_CTRL_TCIE)
}
}
if ((inte & nxp.LPUART_CTRL_TCIE) != 0) && ((stat & nxp.LPUART_STAT_TC) != 0) {
uart.stopTransmitting()
uart.Bus.CTRL.ClearBits(nxp.LPUART_CTRL_TCIE)
}
}
|
