Re: Serial IR receiver problem

[nobody@xxxxxxxxxxxx (Dave Houston)]

andrew@xxxxxxxxxxxxxxxxxxxx (Andrew Gabriel) wrote:

>I suspect that the USB driver (or possibly the Skype application)
>is preventing the serial port driver from emptying the 16550A FIFO
>before it wraps, resulting in lost characters. At 115200, the serial
>port driver must service a 16550A almost once every millisecond to
>avoid character loss. What speed is your IR interface? Do you have
>any flow control? Can you run it at a lower speed to see if that
>helps? I'm not familiar with how Windows handles serial ports, but
>on Unix systems, the serial port driver's interrupt handler is
>normally one of the highest interrupt priority interrupt handlers,
>and that's for a good reason, as 16550A type ports have more
>taxing real-time demands than every other peripheral on a standard
>PC system.

Look at the schematic.

With this hardware, WinLirc treats the DCD line as a digital input - it has
nothing to do with the RS232 data line nor the FIFO. It's messing with the
timer and/or disabling interrupts.