Monday 31st March 2014
See Introduction for pictures.
So, I have most of the Jack Door working, bit I am totally unsure of is RF ID Reader. I created the board based upon U2270 RF ID Reader chip and all the documents I could find on it.
Docs are not that good, or I'm not good enough to read them properly, too much theory, not enough practical for me. So I winged it (as usual in such cases). First attempt at making PCB was a disaster, but 2nd attempt good. Then I had to move Computer and printer into Garage while Grand Children had an extended stay. Somewhere on the way, I mislaid my test RF ID Pet tag (bought from local vet). Found this week-end.
Ok, so I put it off for a while then plugged it all together and powered it up. Lots of teething troubles, lots of re-reading specs. But eventually it was doing something. Son bought a DS203 pocket Oscilloscope some time back. Attached that, voltage pp was 30V, nice, but frequency was way off, I needed 134.2 kHz, calculated as 7.45 uS wavelength, I could adjust down to 11.4 uS before signal started to collapse. Re-visited wound Ariel (roughly 30 turns from memory), removed 1 turn, wave length lower, ended up removing about 12 turns before the frequency was low enough to adjust.
Now put scope onto output, looked like nothing but noise, played lots with software and scope before I got break through tonight. Putting tag within 2 inches of Ariel, I got close wave form, removed it, got wide wave form. Damned thing is actually working :-) Dead chuffed.
Ok, so range is bad, I'd like at least 1 metre, but 2 inches will do for development, get the thing reading, then I can do repeat reads and tune PCB properly.
The rest of tonight I spent capturing output signal and trying to decode into FDX-B format. That I now have, I am happily reading the test tag :-)
Next step is to modify software, I want to keep the reader so that I can use it to read Jack's chip, but I also want it to run as standard, power up Rf ID board, read chip, good or bad flag, power down. Rinse and repeat every second. A good read opens door (like pressing button to open), 3 bad reads in a row closes door (like pressing button to close). Keep test tag code and Jack codes in constants.
Should work, so on the way to Jack Door completion, basically just Donkey work remaining.
