Originally Posted by
luluFRA
perfect, we are waiting to order one !
On the 112 post, we see the Payalneg RC4 transponder, so why your decoder don't support RC4 ?
I have some rechargeable transponders, and they haven't the same preamble than personal transponder : valid signal don't go up.
So, the howard decoder does not support RC4 and rechargeable chips because preambles are different?
For the SPI converter problem, Have you stopped your research?
Today only 8 bits are decoded by the microprocessor, D7 to D0 are used by the decoder preamble and not by the microprocessor, is it correct ?
thanks.
These are all excellent questions!
The Cano decoder does not support the MyLaps RC4 transponders, for two reasons. First, the preamble is different. This, by itself, is not an insurmountable problem, as the circuitry could be modified to accept either preamble (or both) as valid. (Out of curiousity, I had already temporarily modified my decoder breadboard to receive just the RC4 transponder messages.) Second, and more importantly, the Cano decoder requires the transponder to send three identical messages in a row for the message to qualify as a transponder ID. The RC4 doesn’t do that; it sends a very large number of different messages, each repeating only occasionally, and none in a row. (This is an obvious way to make “cloning” very difficult.)
It would not surprise me if our very talented Payalneg has determined the data format for the RC4, which would permit him to use it with his system. Hopefully he will respond to this question.
I don’t have any access to the old AMB rechargeable transponders, so I don’t know what their transmissions look like. They are so old and rare now, that compatibility with them was not one of my design goals. Rather, I was targeting the many thousands of AMB and MRT personal transponders that exist. If the personal transponders are too difficult or expensive to obtain for your club, then you should consider using the Cano transponders.
Microchip has been unable to resolve the microprocessor’s SPI problem, so I used external components (labeled “PARALLEL INTERFACE” on the microprocessor schematic sheet) that perform the same function.
The microprocessor reads 24 bits of the transponder transmission after the 16 bit preamble. These 24 bits are brought into the microprocessor as bytes via the parallel interface.
Originally Posted by
luluFRA
somes pictures :
FPGA board (ebay at $25) ,howard loop detector and PDIA.
I don't see always the same hex code, transponder always send only one message ?
That looks great!
The transponder can send up to about nine different messages. It sends the one which we are using for ID at least three times consecutively, then sends some type of status message on the next transmission. This means that the decoder needs to determine whether the message is for ID or status. Since we have no way of knowing what the message means, the decoder keeps a list in memory of the newest 10 messages that have been received at least 3 times consecutively. If the message matches one in this list, then it is used for ID. If there is no match, then the message is ignored.