Hi Miguel,

Rodel Miguel wrotes on Mittwoch, 8. Dezember 2004 07:42:

I am porting U-Boot to a custom board (ARM920T) and I have to do something about the UART (ns16550.c) driver to support (I know WD would disagree with this :p) XON/XOFF. I have to do this because my board can support only < 19200 baudrates. At 19200 baudrate, I have a

Hm, it should work better with lower baud rates, not worse.

functional serial console but downloading binaries using loadb, kermit would always say that the remote host is not reponding (ERROR: Remote Kermit Not Responding). I debugged this on the getc level and verified that my board's U-Boot can accept the first few data from my PC's kermit and then the loadb function hangs, i.e. does not accept any data. I think this is because my UART's FIFO is not handled well, and probably needs software flow control.

I don't think software flow control is much of help. If your interrupt routine would be fast enough to send an XOFF to the host bevore your FIFO overflows, it should also be fast enough to read your FIFO and copy the received Bytes to RAM bevore an overflow occours.

Since U-Boot drivers normally don't use interrupts, a serial driver which polls the FIFO (the receive register) should be OK and fast enough, not to swallow bytes.

I have a running Board with ARM920T CPU. There the loadb command works well with a polling driver at 9600 Baud.

Regards, Martin