96e863f0f3
This can be very useful for some purposes:
* It makes it possible to disable the UART in cases where it is not
needed or needs to be disabled to conserve power.
* It makes it possible to disable the serial output to reduce code
size, which may be important for some chips. Sometimes, a few kB can
be saved this way.
* It makes it possible to override the default, for example you might
want to use an actual UART to debug the USB-CDC implementation.
It also lowers the dependency on having machine.Serial defined, which is
often not defined when targeting a chip. Eventually, we might want to
make it possible to write `-target=nrf52` or `-target=atmega328p` for
example to target the chip itself with no board specific assumptions.
The defaults don't change. I checked this by running `make smoketest`
before and after and comparing the results.
46 строки
1,2 КиБ
Go
46 строки
1,2 КиБ
Go
package machine
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import "errors"
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var errNoByte = errors.New("machine: no byte read")
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// UARTConfig is a struct with which a UART (or similar object) can be
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// configured. The baud rate is usually respected, but TX and RX may be ignored
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// depending on the chip and the type of object.
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type UARTConfig struct {
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BaudRate uint32
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TX Pin
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RX Pin
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}
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// NullSerial is a serial version of /dev/null (or null router): it drops
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// everything that is written to it.
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type NullSerial struct {
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}
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// Configure does nothing: the null serial has no configuration.
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func (ns NullSerial) Configure(config UARTConfig) error {
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return nil
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}
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// WriteByte is a no-op: the null serial doesn't write bytes.
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func (ns NullSerial) WriteByte(b byte) error {
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return nil
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}
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// ReadByte always returns an error because there aren't any bytes to read.
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func (ns NullSerial) ReadByte() (byte, error) {
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return 0, errNoByte
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}
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// Buffered returns how many bytes are buffered in the UART. It always returns 0
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// as there are no bytes to read.
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func (ns NullSerial) Buffered() int {
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return 0
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}
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// Write is a no-op: none of the data is being written and it will not return an
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// error.
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func (ns NullSerial) Write(p []byte) (n int, err error) {
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return len(p), nil
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}
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