RX and TX Buffers for HardwareSerial are hard coded in size and equal length

[jantje]

Hi
I have many arduino sketches that send out lots of data and hardly receives any data.
I really would like to increase the TX buffer but not the RX buffer. Therefore I would like to modify the HardwareSerial class where it states:

#if (RAMEND < 1000)
  #define SERIAL_BUFFER_SIZE 16
#else
#if ARDUINO_AVR_MEGA2560
#define SERIAL_BUFFER_SIZE 64
#else
  #define SERIAL_BUFFER_SIZE 64
#endif
#endif

to

#if !(defined(SERIAL_TX_BUFFER_SIZE)&&defined(SERIAL_RX_BUFFER_SIZE))
#if (RAMEND < 1000)
#define SERIAL_TX_BUFFER_SIZE 16 
#define SERIAL_RX_BUFFER_SIZE 16 
#else
#if ARDUINO_AVR_MEGA2560
#define SERIAL_TX_BUFFER_SIZE 64 
#define SERIAL_RX_BUFFER_SIZE 64 
#else
#define SERIAL_TX_BUFFER_SIZE 64 
#define SERIAL_RX_BUFFER_SIZE 64 
#endif
#endif

this allows to change the size by using a define and allows for different sizes for RX and TX buffer.
and make all subsequent changes.
Would a change like this be accepted?
jantje

[jantje]

due to #1870 and #1856 sizes bigger than 255 have no use.
I remember having seen a issue about the memory usage of the serial buffers when not used (I know they take memory when not used due to the extern declaration) if that issue is fixed maybe it is smarter to change the buffersize on the mega to a default of bigger than 64?

[jantje]

as fixed in #1955

[mrts]

@jantje But how do you actually use it with Arduino IDE? Would

#define SERIAL_TX_BUFFER_SIZE 32
#include <Arduino.h>

at the top of a .ino file work (I doubt as AFAIK Arduino.h is implicitly included)?

[matthijskooijman]

@mrts, that won't work, since those defines will not be in effect when HardwareSerial0.cpp, which defines the actual buffers, is compiled. I think the way to do this right now, is to modify HardwareSerial.h.

[mrts]

@jantje, right, that's what I expected. Thanks for clarifying!

[jantje]

you can also modify platform.txt or boards.txt
It may be a good idea to make a "big buffer" board.

[mrts]

Thanks for the tip!

[PaulStoffregen]

You can also create a menu using boards.txt, with each option in the menu passing different -Dxyz flags to the compiler.

[YsHoang]

How i can change buffer of arduino due?