Problem with Receiving data at 1MBps ( 1000000bps)

Forum 2005-2010 (read only) Software Troubleshooting
4

Hi ksamay,

1Mbps / 10 bits/char = 100000 chars/s
16 MHz / 100000 chars/s = 160 CPU cycles per character

receiving at 1 MBps requires a very tight timing and even disabling IRQs for a very short time (1 character = 160 CPU cycles) is enough for the serial receive ISR to lose data.

This means:

  1. avoid to disable IRQs whenever possible
  2. if you have to disable IRQs, keep the the time as short as possible
  3. the same as #1&#2 for other ISRs, e.g. the timer IRQ used for millis()/micros()

The timer ISR is called every 1024 microseconds and it might take more than 160 CPU cycles. When you don't need the time functions, you can disable the timer ISR:

      cbi(TIMSK0, TOIE0);

Please try if this fixes your problem.

MikeT