Wire close to pickup has connectivity, just need to splice new cable I hope; erratic behavior of card reader interface

 ATTEMPTING TO RESCUE THE MAGNETIC PICKUP

I figured out how to release the three pins from the PCB connector, releasing the cable from the magnetic pickup. It has two wires plus an outer shield. As before the ends of the wires measured as an open circuit.

The pickup is mounted in a holder with an allen head setscrew to lock it in position. It has to be adjusted to sit .007" from the ends of the teeth on the timing wheel. I released the setscrew and withdrew the pickup from the holder.

No amount of wiggling of the wires restored connectivity. At this point, I would either have a break somewhere down the several inches of cable or inside the pickup itself. I decided to remove the majority of the cable and get access to the wires just as they left the molded plastic of the pickup.

I was very pleased to find that after stripping insulation off of the 1/4" of wire remaining, there was a resistance of approximately 635 ohms across the two wires and it seemed solid as I moved the wires around. 

I am hopeful that if I splice on some replacement cable, I will have a functional pickup again. Time to look for a cable with suitable impedance characteristics. 

TESTING THE CARD READER INTERFACE WITH THE WORKING M600 READER

Since my Model 600 reader was working perfectly the last time I used it, but the very ad hoc interface was giving me issues, I decided to create a new version of the external box. The board I had soldered up for that was not communicating properly with the laptop, garbling characters. I thought that I had a board that communicated well already inside the M1000. It was simple to unplug that from the new reader and stick it into the external box I had recently built.

Indeed, the board talked well with my laptop, tested first with a terminal emulator program (PUTTY) and then with the cardread.exe program that Brian Knittel wrote. I connected the cable and did some testing with the M600 card reader. Alas, the interface would get hung up after reading a card. In fact, the data it stored had the actual holes on the card but many spurious holes as well. 

It would then hang with what the microcontroller thought was an active pick command but the card reader itself disagreed. If I reset the reader or power cycled it, the microcontroller would report an unexpected pick response. 

I also did a pick using PUTTY, which gave me the 160 bytes of data and a final status character. Something is not right here and I am suspecting, since the pick error character is similar to how the M1000 presented back when I tried to drive it with the controller, that the interface is being corrupted by spikes or induced voltages as the card reader operates. This would explain why it starts out working perfectly with the reader until we fire up the motor and read a card.