softserial - buffer too small easily...

Projects Networking, Protocols, and Devices
1

Hi,
I have used the softserial to read from some sensor and write it out via the serial port -> modem -> receiving computer online.
Using an pro 3.3v 8mhz and running the serial and softserial ports with 9600 it seems that the processor cannot catch up sending the data out on the serial port it receives in the softserial.
I use simple method as described in the documentation:

if softserial.available()
serial.write(softserial.read());
I got checksum errors all the time until I made the buffer bigger in sorftserial.h
The sensor does not send a lot of data in one go but more than 64 bytes I guess which the buffer is set to by default....
I guess it might send 150? at a time...
Anyway changing the buffer to 256 bytes seems to have solved the problem.
Also this all seems obvious to me now but it took me a while to figure out where the problem was - so I thought I report this .

I guess it would be nice if in the documentation it was mentioned that one gets buffer overruns that easily... and that this can be remedied (in some cases) by making the buffer bigger.

What if one wants to transmit bigger amounts of data this way. Can one control the data sent to the soft-serial somehow using the stop bit?
Or can one make that buffer very big - lets say 16 kbytes?

cheers
sigi

2

Or can one make that buffer very big - lets say 16 kbytes?

No, that's impossible because your processor only has 2kB of RAM.

I guess it would be nice if in the documentation it was mentioned that one gets buffer overruns that easily... and that this can be remedied (in some cases) by making the buffer bigger.

That's not a problem of the buffer, it's an inherent problem of SoftwareSerial. It should be documented to not use that class unless you exactly know what you're doing and you have no other way to solve the problem of having a missing UART.
The SoftwareSerial class is blocking interrupts during the complete reception or send process. For the hardware serial interface interrupts are used to feed the next byte from the sending buffer into the hardware register or store the next byte from the hardware register in the reception buffer. So it's kind of a dilemma not easily solvable. If it's possible in your case try using AltSoftSerial (AltSoftSerial Library, for an extra serial port) because that implementation doesn't block interrupts but uses a timer and is limited to fixed pins.