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Asked: 2026-05-13T09:02:56+00:00

This question is related with Microcontroller programming but anyone may suggest a good algorithm

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This question is related with Microcontroller programming but anyone may suggest a good algorithm to handle this situation.

I have a one central console and set of remote sensors. The central console has a receiver and the each sensor has a transmitter operates on same frequency. So we can only implement Simplex communication.

Since the transmitters work on same frequency we cannot have 2 sensors sending data to central console at the same time.

Now I want to program the sensors to perform some “polling”. The central console should get some idea about the existence of sensors (Whether the each sensor is responding or not)

I can imagine several ways.

  1. Using a same interval between the poll messages for each sensor and start the sensors randomly. So they will not transmit at the same time.

  2. Use of some round mechanism. Sensor 1 starts polling at 5 seconds the second at 10 seconds etc. More formal version of method 1.

The maximum data transfer rate is around 4800 bps so we need to consider that as well.

Can some one imagine a good way to resolve this with less usage of communication links. Note that we can use different poll intervals for each sensors if necessary.

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  1. Editorial Team

    I presume what you describe is that the sensors and the central unit are connected to a bus that can deliver only one message at a time.

    A normal way to handle this is to have collision detection. This is e.g. how Ethernet operates as far as I know. You try to send a message; then attempt to detect collision. If you detect a collision, wait for a random amount (to break ties) and then re-transmit, of course with collision check again.

    If you can’t detect collisions, the different sensors could have polling intervals that are all distinct prime numbers. This would guarantee that every sensor would have dedicated slots for successful polling. Of course there would be still collisions, but they wouldn’t need to be detected. Here example with primes 5, 7 and 11:

     ----|----|----|----|----|----|----|----| (5)
 ------|------|------|------|------|----- (7)
 ----------|----------|----------|-:----- (11)
                                   * COLLISION

    Notable it doesn’t matter if the sensor starts “in phase” or “out of phase”.

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