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//go:build atmega || esp || nrf || sam || sifive || stm32 || k210 || nxp || rp2040 || rp2350
package machine
import "errors"
var errUARTBufferEmpty = errors.New("UART buffer empty")
// UARTParity is the parity setting to be used for UART communication.
type UARTParity uint8
const (
// ParityNone means to not use any parity checking. This is
// the most common setting.
ParityNone UARTParity = iota
// ParityEven means to expect that the total number of 1 bits sent
// should be an even number.
ParityEven
// ParityOdd means to expect that the total number of 1 bits sent
// should be an odd number.
ParityOdd
)
// To implement the UART interface for a board, you must declare a concrete type as follows:
//
// type UART struct {
// Buffer *RingBuffer
// }
//
// You can also add additional members to this struct depending on your implementation,
// but the *RingBuffer is required.
// When you are declaring your UARTs for your board, make sure that you also declare the
// RingBuffer using the NewRingBuffer() function when you declare your UART:
//
// UART{Buffer: NewRingBuffer()}
//
// Read from the RX buffer.
func (uart *UART) Read(data []byte) (n int, err error) {
// check if RX buffer is empty
size := uart.Buffered()
if size == 0 {
return 0, nil
}
// Make sure we do not read more from buffer than the data slice can hold.
if len(data) < size {
size = len(data)
}
// only read number of bytes used from buffer
for i := 0; i < size; i++ {
v, _ := uart.ReadByte()
data[i] = v
}
return size, nil
}
// WriteByte writes a byte of data over the UART's Tx.
// This function blocks until the data is finished being sent.
func (uart *UART) WriteByte(c byte) error {
err := uart.writeByte(c)
if err != nil {
return err
}
uart.flush() // flush() blocks until all data has been transmitted.
return nil
}
// Write data over the UART's Tx.
// This function blocks until the data is finished being sent.
func (uart *UART) Write(data []byte) (n int, err error) {
for i, v := range data {
err = uart.writeByte(v)
if err != nil {
return i, err
}
}
uart.flush() // flush() blocks until all data has been transmitted.
return len(data), nil
}
// ReadByte reads a single byte from the RX buffer.
// If there is no data in the buffer, returns an error.
func (uart *UART) ReadByte() (byte, error) {
// check if RX buffer is empty
buf, ok := uart.Buffer.Get()
if !ok {
return 0, errUARTBufferEmpty
}
return buf, nil
}
// Buffered returns the number of bytes currently stored in the RX buffer.
func (uart *UART) Buffered() int {
return int(uart.Buffer.Used())
}
// Receive handles adding data to the UART's data buffer.
// Usually called by the IRQ handler for a machine.
func (uart *UART) Receive(data byte) {
uart.Buffer.Put(data)
}
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