It is quite common on many industrial serial devices which do not support either software or hardware flow control to require a Inter-Character delay longer than than the standard one, one and a half, or two stop bits. A device where this long inter character delay is required are devices like Point of Sale terminals, and devices that are talking to Modbus (Honeywell SI-FTA implements a check on the inter-character gap). Some hardware manufactures have seen this need, and added it to their UART controllers - Atmel's AT32AP7000 has added this and called it a "Timeguard" (Don't ask me why). The "timeguard delay" is controlled between 0 and 255 Bit Periods. http://www.atmel.com/dyn/resources/prod_documents/doc32003.pdf I think I have seen similar things for some ARM devices, and other embedded architectures. Today, we have done similar things in the driver (on hardware that doesn't support it natively). I'm not sure that bit periods are the best way to measure things, or milliseconds. I guess it really doesn't matter, as long as everyone does it the same way - which brings me to my next question: Does anyone have a good idea of a standard way to expose this to userspace? - grabbing 8 bits in the termios_p c_oflag isn't going to fit - adding a new field in the termios structure seems like overkill - adding backdoor ioctls for serial drivers seems like a bad idea. Thoughts? Thanks -Robin - To unsubscribe from this list: send the line "unsubscribe linux-serial" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
