HE433/HE8

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Jan Lichtenbelt
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HE433/HE8

Post by Jan Lichtenbelt »

In Elektuur of September 1998 (very old already!) there has been published a 433 MHz sender/receiver. Up to now I use it with pleasure to switch my garden railway tournouts. I want to replace just the transmisster by a modern one. But I do not know the protocol used betwen the transmitter and receiver. Does someone can help me?
The transmitter is HE433-1/T or 10/T and the receiver HE433-2R and the microcontroller used, is HE8. All of the firm Heilander Electronic.

With kind regards

Jan Lichtenbelt

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Steve001
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Re: HE433/HE8

Post by Steve001 »

Hi Jan,

I have an old 1980's electronics magazine from maplin that has a project for a railway control similar to a DCC system .
It goes into some depth on how and why it works, i do know that the receiver chips are now obsolete now but this should be creatable within flowcode.
This is a project that i would like to do but i haven't got the time at the moment.

I can scan the magazine at work if you wish next week sometime

Steve
Success always occurs in private and failure in full view.

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Jan Lichtenbelt
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Location: Haren GN, the Netherlands
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Re: HE433/HE8

Post by Jan Lichtenbelt »

I puzzled myself and found the HE protocol. It is:
1) 2 start bytes (0x01 and 0x02)
2) 2 address bytes
3) 2 data bytes
4) 2 control bytes
5) 4 bytes off
with a bit time of about 108 usec and byte time 866 usec and a total time of about 9080 usec, see details the attached file.
Do someone knows what the algorithm could be for the control bytes?

With kind regards

Jan Lichtenbelt
HE433_protocol.xlsx
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Jan Lichtenbelt
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Location: Haren GN, the Netherlands
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Re: HE433/HE8

Post by Jan Lichtenbelt »

After a lot of puzzeling, the solution was found to be simple!

4 bytes will be sent as 4 words (16 bits), each with a start bit and a parity bit like:
S=1, 7bits, P(even), 5bits=0

The first byte is empty, the second is the address byte, the third the data byte and the last the control byte
Then no signal will be sent during the period of 4 bytes.

The bit time is about 108 µsec. But there is a lot of time fluctuations the signals. That means triggering on each new start bit is recommended.

The control byte = address byte + data byte +1 with the byte readed from left to right. That means the LB byte will be sent first and the MB last.

Jan Lichtenbelt

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