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Correct SampleTime for PacketOutput to Virtual COM-Port

Asked by S on 12 Jan 2013

I'm using a packet output block in a rtwt simulink model to send data via an usb-to-uart interface to my target hardware. The detail I'm a bit confused about is which is the correct sample time. After experimenting a bit with packet input I figured out to use sendrate/packetsize in order to receive my data correctly (more precisely to detect the startflag). On the other hand all inputs of my packet output block are set with most recent data at all time so it could send them out all at once. I want to send 54 bytes 50 times per second Which is the correct sampletime for my packet output block and why: sendrate or sendrate/packetsize?

Thank you all in advance

0 Comments

S

1 Answer

Answer by Jan Houska on 14 Jan 2013
Accepted answer

If you want to send out 54 bytes 50 times per seconds, then it is best to send one packet consisting of those 54 bytes with a sample rate of 0.02. This way, there's minimum load on the CPU and as much work as possible is offloaded to the serial port hardware.

Also, please ensure that your serial port baud rate is sufficiently high. To be able to send 27000 (54*10*50) bits of data per second, your baud rate should be at least 38400, but even higher would be better.

1 Comment

S on 20 Jan 2013

Thanks a lot for your answer, its working perfectly now. Maybe the expression "...and interact with the I/O hardware" in the docs was a bit too confusing here.

Jan Houska

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