This is a picture of the complete KBSnoop card. As you can see we have finally made a real PCB for it.
Hardware
So, what makes the KBSnoop work? Well, it is a small PCB containing a microprocessor and a couple of extra components to connect it to the PC, keyboard (or PS/2 mouse) and a serial port.
PCB
The PCB card for the KBSnoop consists of a microprocessor from Atmel, an AT90S2313 (1.8MB pdf specification) running at 3.6864 MHz. The processor includes 2kB flash memory for the program, 128 bytes EEPROM for configuration data and 128 bytes of RAM.
To this processor, a MAX232CPE RS-232-transmitter-receiver is connected which is used to convert the TTL signal levels to RS-232 signal levels. The MAX232 circuit uses a couple of electrolytic capacitors. They must all be of the value 1.0µF/16V.
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This is a picture of the complete KBSnoop card. As you can see we have finally made a real PCB for it. |
For those of you interested in how things are connected on the CPU-card, here is a logical drawing of it, and here is a pdf-file (11 kB) of the layout drawn in Protel-99.
Here is a list of components needed to build the KBSnoop-card:
| Item | # of pieces | Price | Total Price |
|---|---|---|---|
| Atmel AT90S2313 CPU | 1 | $5.00 | $5.00 |
| MAX232CPE RS-232-transmitter-receiver | 1 | $2.50 | $2.50 |
| 3.6864 MHz crystal | 1 | $2.50 | $2.50 |
| 6-pin IDC connector | 1 | $2.00 | $2.00 |
| 6-pin mini-DIN connector (female) | 2 | $3.50 | $7.00 |
| 9-pin D-Sub connector | 1 | $2.00 | $2.00 |
| 10pF ceramic capacitor | 2 | $0.20 | $0.40 |
| 1.0µF electrolytic capacitor (16V) | 5 | $0.25 | $1.25 |
| 1kW resistor | 2 | $0.10 | $0.20 |
| 1 LED | 1 | $0.20 | $0.20 |
| Total price | $23.05 |
I am sure that it is possible to find the above components at a lower price, I just took the prices right out of the ELFA catalog and they are not always the cheapest to buy from.
Besides the components listed above you also need the following:
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Something to build the thing on, for example a prototyping board |
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A couple of IC-sockets if you don't want to solder directly on the IC's |
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Some wire |
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Soldering equipment |
Hopefully that's all you need to build one, if I have forgotten something, please tell me!
Connecting KBSnoop to the PC
Connecting the KBSnoop to the PC is pretty easy, do like this:
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Connect the keyboard (or PS/2 mouse) to one of the KBSnoop 6-pin mini-DIN connectors (it does not matter which DIN-connector you connect it to). |
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Connect the other 6-pin mini-DIN connector to the PC using a cable with male mini-DIN connectors in both ends. |
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Connect the 9-pin D-Sub connector to the PC's serial port using an ordinary serial cable for the PC (NOT a null-modem cable). |
That's it! Now you need to start some sort of terminal program (for example Windows HyperTerminal) on the PC to display the data that KBSnoop sends to the PC's serial port.
Error indication
Even though KBSnoop has a LED, no error indication is ever displayed on it. The LED is simply there and blinking to let you know that KBSnoop is working as it should. If it stops blinking, the KBSnoop software has stopped executing and it has to be reset.
