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grassrootkit15-Mar-09 0:02
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GeneralRe: Doc /View Debugging. Pin
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GeneralRe: Doc /View Debugging. Pin
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QuestionSerial port read latency (SERIOUS - NEED HELP FAST!) Pin
PeniWize14-Mar-09 14:24
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AnswerRe: Serial port read latency (SERIOUS - NEED HELP FAST!) Pin
Luc Pattyn14-Mar-09 15:21
mvpLuc Pattyn14-Mar-09 15:21 
Hi,

welcome to CodeProject. And, good first post!

first of all it is very ambitious to mention Windows, real-time and 5 or 20 msec all in one sentence.

I do have quite some experience with Windows serial ports, it is getting a bit rusty though. Amongst others, I did a serial protocol where overall bandwidth was most important, but so was latency time for the first message. So I did experiment with all the timeout parameters a lot.

The scheme you described seems rather complex, and makes me wonder how the hell you can ever test that to satisfaction as data can and will come in asynchronously with respect to your 5msec operations, which (1) may interfere with the driver's normal operation, and (2) may have some timing jitter.

BTW: how do you create that 5msec period?

Although you did describe a lot, I would want to know more, such as: Is it binary data, or text (8-bit or 16-bit)? How many bytes or characters would make up a single message? is throughput relevant, or just latency? why did you choose 19200 Baud? would it be possible to change the protocol? and the port's settings?

Also I wouldn't mind some background info, what it really is about; it tends to help me focus on the technical solution when I know what kind of application is involved.

Give me some more info, and I'll probably come up with a direction I would be inclined to take, to get something both simple and hopefully as reliable as Windows can offer.

Smile | :)

Luc Pattyn [Forum Guidelines] [My Articles]

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GeneralRe: Serial port read latency (SERIOUS - NEED HELP FAST!) Pin
PeniWize14-Mar-09 20:48
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GeneralRe: Serial port read latency (SERIOUS - NEED HELP FAST!) Pin
Luc Pattyn15-Mar-09 4:49
mvpLuc Pattyn15-Mar-09 4:49 
GeneralRe: Serial port read latency (SERIOUS - NEED HELP FAST!) Pin
PeniWize15-Mar-09 10:13
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GeneralRe: Serial port read latency (SERIOUS - NEED HELP FAST!) Pin
CPallini14-Mar-09 23:59
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AnswerRe: Serial port read latency (SERIOUS - NEED HELP FAST!) Pin
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GeneralRe: Serial port read latency (SERIOUS - NEED HELP FAST!) Pin
PeniWize14-Mar-09 20:55
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GeneralRe: Serial port read latency (SERIOUS - NEED HELP FAST!) Pin
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GeneralRe: Serial port read latency (SERIOUS - NEED HELP FAST!) Pin
grassrootkit14-Mar-09 23:29
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GeneralRe: Serial port read latency (SERIOUS - NEED HELP FAST!) Pin
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GeneralRe: Serial port read latency (SERIOUS - NEED HELP FAST!) Pin
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GeneralRe: Serial port read latency (SERIOUS - NEED HELP FAST!) Pin
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AnswerRe: Serial port read latency (SERIOUS - NEED HELP FAST!) Pin
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AnswerRe: Serial port read latency (SERIOUS - NEED HELP FAST!) Pin
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