Thanks for your reply maeg,
I know that the transponders work with AMB as well.
How long have you made your loop?
Our track is 10m wide, so the loop wire will have to be 20m long.
Howard, Would the amplifier and decoder be able to work on such a long loop?
Is anyone already using the system sucsessfully with such a long loop?

No, it's too long. Our is 7.5m wide and we have problems without changing amplifier capacity.

I agree with maeg. 10m is far too big. That's about twice the original design limit.

2 garycapetown
You don't need to do loop on widest part of track - take it to the one of tight turn.

The thread has reached another milestone. We now have more views than the very widely-read thread complaining about "AMBrc's overpriced transponders".

Do we have a CLPD yet?
And if we do can I get a copy of the programming or a chip.

I can hand solder most surface mount devices over .05 but prefer .08 64pinTQFP.

I have been watching this project from day one and I am really impressed with the progress. At one point I was thinking of using a Xmega for the decoder but even at 48Mhz and in machine language the Xmega would be to slow and the TTL chip solution is a great idea but to big for my taste. The CLPD is the way to go ,I would rather spend $25.00 for one chip then point to point solder 15+ chips.

The Arduino shield is a neat idea for Hobby level designs but I would rather develop my own hand held timing system in a 2 chip solution that would output AMB compatable packets. then I can use one of the many timing systems that are out there.

A number of us have implemented the decoder with a CPLD. See my post earlier in this thread. I started by implementing Howard's logic, then simplified a few bits, added CRC generation and used a simple SPI output to the microcontroller.

Later this year I'll be implementing the whole thing in an FPGA with multiple channels, event timestamping and data buffering. First I'm trying to simplify the input amplifier.

Is it possible to give the SPI signal characteristic ?
number of bit, parity, SPI mode, clock polarity, data is capture on clock's rising edge or falling edge ?

Thanks.

See this post for a description of the SSC:

http://www.rctech.net/forum/radio-el...l#post11880840

Data should be captured in on the positive-going edge of SSCLK, or the negative-going edge of /SSCLK.

The schematic you show was for a previous hardware revision, which created a slave select signal and gated clock for the PIC microprocessor. In this case, data should be captured on the positive-going edge of SCL.

There is no particular number of bits. The bits are presented serially with no delays between bytes, words, or any other groupings. The data stream will continue as long as valid data is received. Since there is no particular grouping of bits, there is also no parity bit.

It is up to you to determine what operating mode on your microprocessor will support the data stream presented to it.

On a related note, I recently heard from Microchip regarding the problems I had with their SPI module. I had previously posted that I could not get their module to work when running at the maximum serial clock frequency specification, despite all timing requirements being met. Microchip has confirmed the problem. I'm sure it will take a new silicon revision to fix it, but I don't think that's in their agenda, since the current silicon has existed for quite a while, and I was the first one to report the problem to them.

Hello Howard!
Our winter season is in hot time.
Could you explain, please, about capacity of loop?
We have some problems with signal quality, Payalneg added to the firmware option to display signal quality for each time it detects transpoder - so now I can see it on track in real time.
I need to tune my loop better. The only thing I can try - is changing wire of the loop and capacity.
Maybe some rules for changing capacity? When I need to take bigger capacitor or smaller?

The loop tuning is not very critical, so following the recommendations given in post #251 for capacitance versus loop size should suffice:

http://www.rctech.net/forum/12222187-post251.html

In general, a larger loop will require less capacitance to keep it resonant at about 5 MHz.

You can verify that the tuning is correct by monitoring the output of the loop amplifier (R11 pin 2) using an oscilloscope with AC coupling. Place a transponder above the center of the loop, high enough to reduce the loop amplifier output to about 10mV peak to peak, then adjust the loop capacitance for maximum carrier output.

Thank youm Howard.
If I only have an oscilloscope
Now I can see if it is OK or not only by Signal Quality displayed at decoder, but rule large loop less capacity is what I was need

I have encountered the same problem two races in a row now... Everything works great all day long and then at about the 11-12th hour of my race program... Mylaps RC4 Decoder box is not taking in anymore laps. If i reboot the box it starts working again... I have been tempted to clear passing on the box but figure it would be much better to ask here- I really only mess with the squelch on the box-
What is going wrong...
Also what if any maintenance to the box is needed?

Thanks guys!

I think you'll receive more helpful advice if you post your questions on a thread whose subject is the MyLaps RC4 system. Or you could also start a new thread. There are plenty of knowledgeable RCTech readers who are happy to share advice.

The disadvantage in posting here is that this thread is not about the RC4 decoder, so you may not get many responses.

Myself being an electronics novice, I need to ask, would it be a huge design change to get longer loop lengths?

I could see potential interest from other forms of racing (ie. auto, motocycle, etc) if the loop could accomodate greater lengths and transponders could send greater distances.