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Mozfet

Need for speed?

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We have 4 K3HB communicating to a SCU (RS485). The speed is 38400 bps. Now, we have 1 / 38400 * 10 = 260us for transfering a byte. The packet is about 20 bytes which makes about 5ms. 5ms * 4 K3HB devices should give 20 ms. But the practise shows something different - 7-8 readings for 1s??? How can we achieve that 20 ms?

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The protocol is master/slave so there are two transmissions per node. The calculation would be master overhead + 20 bytes of transmitted data@38400 bps + slave overhead + 20 bytes of response data @ 38400 bps. I think you will find that the master and slave overhead contribute much more to the calculation than the speed of data transportation. 7-8 reads per second does not sound unreasonable.

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