> I am trying to transfer 256 bytes of at data 1M baud rate from my PC to a=
n Atmega328
> microcontroller. I am using checksum to verify the integrity of the data =
and I am
> emptying the received data into a ring buffer as quickly as possible. Thi=
s is all I
> have in my interrupt subroutine:
> temp =3D UDR0;
> BufferWrite(&rx_buffer,&temp);
> The data is transferred properly only at speeds upto 250K baud rate. It r=
esults in
> error beyond that point. The Atmega 328 datasheet specifies that it possi=
ble to
> transfer at speeds upto 2M baud rate. The ring buffer size is about 400 b=
ytes and I
> am looking for some suggestions to achieve higher baud rates while mainta=
ining the
> data integrity.
> Sai

Use assembler instead of C?

At that rate I suspect you should write the interrupt routine in assembler,=
 and use a highly optimised ring buffer architecture where you need to upda=
te only the write pointer, and then the read routine works out how full the=
 buffer is by taking the difference between the write and read pointers. It=
 is possible to do this in a manner that doesn't involve race conditions on=
 the pointers.

I presume the UART can buffer more than one character. Immediately before l=
eaving the interrupt routine I would check to see if there is another chara=
cter ready to be read instead of incurring the overhead of register restore=
 and save before getting the next character.
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