----- Original Message ----- From: "Scott Hannahs" <[EMAIL PROTECTED]> To: "Craig Graham" <[EMAIL PROTECTED]>; <[EMAIL PROTECTED]> Sent: Friday, February 13, 2004 3:29 PM Subject: Re: Serial comms
Thanks all for the responses. > One start bit is the only option. I have never seen a device that uses a different number of start bits. But serial is so screwed up I am sure there is someone out there that decided to use pi start bits! Good to have confirmation on that- I'd never heard of start bits before this. > >Does anyone have any suggestions? > > It seems that your device is not responding because it probably hasn't gotten a "complete message" from the host. Check the documentation to see if there is a message terminator in the command string? Try a carriage return or lf as a terminator. Try EOT as a terminator. Make sure that the string has the correct check sum (sometimes protocols have the checksum include the string lenght tag, sometimes not). I would guess the problem is in carefully crafting the string since you have tried all the hardware options. It *shouldn't* need a terminator since you specify a byte count in the first two bytes of the packet. Check sums should be OK since my checksum generator is producing results consistent with their examples. The terminator has to be worth a try though. > Many systems have a way of snooping on serial port communications. I can give you a good way for Mac OS X...... But I am going out on a limb and guess that isn't your host system! :-) Others can suggest software for various winders versions. Nope, I am indeed on Windows. However I have found a couple of software-based snoopers that I'll try later if shoving a terminator in doesn't help. Glad it's looking like I don't have to write my own analyser. -- Dr. Craig Graham, Software Engineer Advanced Analysis and Integration Limited, UK. http://www.aail.co.uk/
