Adds HardwareSerial::setRxBufferSize()

[SuGlider]

Summary

It adds HardwareSerial::setRxBufferSize() with default value of 256 bytes.
Fixes #5580

Impact

It allows to define a Rx Buffer Size for UART, before begin().

[bertmelis]

uint8_t rxfifo_full_thrhd = 112, size_t rxBufferSize = 256

Isn't this inconsistent?

[szerwi]

I think it will be better to keep similar parameter order that is in the uartBegin() function. So instead of:
unsigned long baud, uint32_t config, int8_t rxPin, int8_t txPin, bool invert, unsigned long timeout_ms, uint8_t rxfifo_full_thrhd, size_t rxBufferSize
I propose:
unsigned long baud, uint32_t config, int8_t rxPin, int8_t txPin, size_t rxBufferSize, bool invert, unsigned long timeout_ms, uint8_t rxfifo_full_thrhd

[SuGlider]

uint8_t rxfifo_full_thrhd = 112, size_t rxBufferSize = 256

Isn't this inconsistent?

Why would it be?
rxfifo_full_thrhld is related to UART RX FIFO (fixed size =128 bytes)
rxBufferSize is related to RX Queue size fed by RX ISR.

[SuGlider]

I think it will be better to keep similar parameter order that is in the uartBegin() function. So instead of:
unsigned long baud, uint32_t config, int8_t rxPin, int8_t txPin, bool invert, unsigned long timeout_ms, uint8_t rxfifo_full_thrhd, size_t rxBufferSize
I propose:
unsigned long baud, uint32_t config, int8_t rxPin, int8_t txPin, size_t rxBufferSize, bool invert, unsigned long timeout_ms, uint8_t rxfifo_full_thrhd

Adding to the end of parameter list will preserve retro compatibility.

[me-no-dev]

I would suggest adding back setRxBufferSize(size_t) which would set a class variable that can then be used in begin, so code like the one below would work. Similar to setPins()

Serial.setRxBufferSize(1024);
Serial.begin(115200);

[SuGlider]

I would suggest adding back setRxBufferSize(size_t) which would set a class variable that can then be used in begin, so code like the one below would work. Similar to setPins()

Serial.setRxBufferSize(1024);
Serial.begin(115200);

Added and commited.
PR name, summary and impact were updated.