JayCar MkII Add on

[Blackbiro]

Here are two pics of add ons you can build into your JayCar MkII programmer.
Both these mods have been well discussed in previous posts so I won't go there again.
Basically these add ons quickly enable you to switch from a MkII to MkI system (DPDT toggle switch) which cures a fault that the MKII thinks the card is not inserted when in fact it is.
The second add on (SPDT toggle switch) is to switch between ACS 1.2 cards and Delta ACS 4.1 cards that some times the MkII won't read using FMCard.
Mod refer:- "gw1 04-03-2005 " for full explaination. Thanks for his good work.
Two pics on link. h.jpg[/IMG]

[gw1]

Nicely done.

It's good you've resisted the temptation to bring the clock frequency jumper out to a toggle switch! That's would be bad idea because the signal on that jumper is high impedance, and the extra load capacitance and noise pickup of a switch and flylead would be bad for stability. There are other ways of modding if you really wanted a remote switch for clock frequency.

[rebnic]

Nicely done.

There are other ways of modding if you really wanted a remote switch for clock frequency.

I cannot even start to comprehend your ability and knowledge, but I just used pcb mounted toggle switches for the frequency and phoenix/smart card switching. It seems to work for me.

[gw1]

Switching clock frequency that way will usually work provided the switch is modern and physically small, and the wires to it are thin and not too long (eg up to 10cm). But it's not good practice. If your mod works then great, enjoy it, but I don't recommend it. There are many, many ways to cut corners in electronics which is why consumer grade products and clones can be so much cheaper than professional grade ones!

The clock is a critical signal for all processors, including smartcards, and poor rise/fall time, ringing, glitches, bad mark/space ratio and high frequency noise can all cause processor instability. In the old days prior to Z80 many processors had dedicated clock generator ICs, such was the criticality of their clocks.

With the Jaycar Mk II, the HC04 inverter in the clock oscillator is biased as a linear amplifier using a high value (1M) feedback resistor, with low value (22pF) load capacitors to prevent the crystal from operating in (eg resonating at 12MHz instead of 6MHz). The reason there's a buffer stage following the oscillator gate is because you don't want noise pickup and the capacitive load of the smartcard and socket upsetting the crystal. That could cause frequency drift, slow startup time, jitter or even oscillation dropouts. The trouble is, hanging a long wire and switch off the jumper link in Jaycar Mk II circumvents the protection that buffer stage is there to provide. It's exactly what you don't want to do. (At least the jumper link is on the output side of the oscillator buffer, not the input side.)

The Jaycar Mk I did clock switching differently, as shown in the schematic . You can replace its jumper link with a remote switch without any problems at all: the jumper link signal is fairly low impedance and not carrying any AC at all.

Another mod approach would be to have separate oscillators (crystal ovens or whatever is convenient), connect the switch to the oscillator output pins, and feed the switch pole back through an HC04 buffer before driving the smartcard clock pin. The buffer would be important in that situation to clean up the (which would be degraded slightly by the capacitance of the cable and switch), and also to normalise the output voltage of any crystal oven(s) being used.

Anyway I hope that helps people understand the issues a little better.

[xfiles_2007]

just wondering , adding a PIC to the reader as a blocker, will it ruin the reader or have any impacts ?

[rebnic]

Picture of my mods. Not technically correct obviously, but works for me.

[rebnic]

Try again.

[gw1]

Picture of my mods. Not technically correct obviously, but works for me

Sorry rebnic, in my previous comment I overlooked where you said "pcb mounted". That will make a difference! Most people using toggle switches mount them some distance away on a front panel or at the rear near the connectors, using flyleads. But using a PCB mount switch as you have done, straight onto the board, is much better. I don't imagine it will cause a problem. Good idea!

just wondering , adding a PIC to the reader as a blocker, will it ruin the reader or have any impacts?

I'm not sure what you mean. Are you thinking of writing your own blocker code, or grafting the PIC from another device onto a Jaycar kit to make a frankenstein interface?

If you're thinking of creating a blocker yourself from scratch then it'll be easier if you start with a blank slate, or a basic Phoenix interface (like Jaycar Mk I) rather than the Mk II which is ill-suited to integration with a microcontroller.

If you're thinking of dismantling an existing blocker product and grafting it onto another design then you'd have to start by studying its circuit and signals to see what it's doing. There's more than one way to go about it and if you don't have the source to the blocker's microcontroller then you have to reverse its behaviour and cater to its requirements. Fun maybe but it'd be quicker to write your own from scrach if you knew what behaviour you wanted.