current community

your communities

more stack exchange communities

Stack Exchange
tour help
Take the 2-minute tour ×
Arduino Stack Exchange is a question and answer site for developers of open-source hardware and software that is compatible with Arduino. It's 100% free, no registration required.
up vote 7 down vote favorite

How does the Arduino handle serial buffer overflow? Does it throw away the newest incoming data or the oldest? How many bytes can the buffer hold?

share|improve this question

migrated from stackoverflow.com May 27 '14 at 15:25

This question came from our site for professional and enthusiast programmers.

1 Answer 1

up vote 7 down vote accepted

For hardware serial ports you can see in HardwareSerial.cpp that the buffer size varies depending on the amount of RAM available on the particular AVR:

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

For a software serial port in SoftwareSerial.h the receiver buffer size _SS_MAX_RX_BUFF is defined as 64 bytes. In both cases it stops attempting to insert received data into the queue when it is full, so you could get a mix to old and new data depending on how you're retrieving data from the queue.

Ideally it would be best to ensure the buffer always gets emptied in a prompt manner to avoid the buffer filling. Maybe take a look at timers and implementing a simple state machine if your problem is related to other code blocking the main loop.

share|improve this answer

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.