Serial interfaces (was Re: Any former Psion 5 owners out there?)

On 7/25/10 2:10 PM, Tony Duell wrote: No, they don't do that. They are manipulated by OS device drivers to provide driver-level interfaces that appear as serial ports. These drivers present the same driver-level API that the drivers for an 8250/16550 sitting on an ISA bus would. On UNIXish systems, they usually appear as /dev/tty* and /dev/cu* like any other serial port, and all the standard ioctl() calls are implemented. They actually work very well; I use them daily and have never had problems with them. Interestingly, some of the higher-end USB<->serial adapters, notably the Keyspan units, are implemented with USB-enabled microcontrollers which can be reprogrammed. If you do this, setting uncommon word widths or baud rates shouldn't be a problem. People are squirting new code into these Keyspan adapters using Linux and free mcs51 compilers like SDCC (a very good C compiler for mcs51, Z80, some PICs, and more, I use it a lot, and I host a chunk of its build farm). Here's a page describing the basics of this: http://www.hhhh.org/wiml/proj/keyspan.html So as you can see, these devices don't really present many restrictions to hard-core hardware hackers. It's just *different*, that's all. Since I've never done much with PCs, I'm not accustomed to dinking around with I/O ports 0x378 and 0x278 directly (and honestly I'd never want to, I don't use PCs here anyway), and that's just about the only functionality that can't easily be implemented by these things. -Dave -- Dave McGuire Port Charlotte, FL