134kHz RFID (animals) not outputing serial data

[BastelBaus]

• Comparable problem to this former one: link
• RFID module for 134,2 kHz - for animals does not output serial data
• some helpful information found link
  • Assume the big IC as a uC and the small one an RFID receiver
• Antenna working and RFID receiver sends data to uC (Pin16)
  --> [1] w/ RFID Tag
  --> [2] w/o RFID Tag

But no serial output. Any idea's how to debug or how to know which chips are used?

[1] w/ tag
cyan: signal @ uC input
magenta: 134kHz signal @antenna output
yellow: serial output pin

[2] w/o tag
cyan: signal @ uC input
magenta: 134kHz signal @antenna output
yellow: serial output pin

[apf1979]

Hmm. I'm guessing because there's no code???

[Whandall]

Some connection between MCU and reader could be useful too.

[BastelBaus]

This board has only a TX and does not need to be controlled. I directly measure the TX by the osci and if there is no signal the uC will also receive nothing.

I think the linked schematic is also not fully correct

• the small IC might be a dual op amp (LM2904) working in single rail mode ?
• the pins of the transistors might be wrongly extracted, I assume PIN 18 is driving the gate of Q1 (which might be wrongly depicted as emitter). ON my scope I see a nice 135kHz square output of the (uC) ?

Very strange, but I would not assume a SW bug and I have two devices both don't work so I would also exclude a HW bug ... I have no Idea how to debug ... finding the uC and try to read the code I have never done and would be a lot of effort ... any ideas ?

[apf1979]

Is the cyan signal a digital IO to let the uC know that information is available?

Does the uC report any serial data received?

Is your time scale set properly? I can see some yellow bits in the images you have. Are you sure the data isn't being compressed too small to see based on your time scale?

[BastelBaus]

Good questions apf1979, thanks.

Yes, I assume the cyan signal to be the input to the uC (saturated output of the OpAmp?). Its a nice 5V signal with a the symbol time of 240us which fits to the standard ( FDX-B )

I have not yet debugged the protocol, but somehow it seams something is wrong within the uC (input, processing, output) ... difficult to debug.

Voltages:

Symbol Timing:

[BastelBaus]

OK, I hooked a nano behind this signal and decoded it with this library, worked very nice with my sureoetcare.com token. However it did not decode the card delivered with the boards (EM4305 Test Card).
... very strange, I don't understand what the bug ...