Hardware Keylogger

[kirtcathey]

Yes, the second drawing is what I am doing. Late last week in a forum exchange with Darrel and after some extensive research, we concluded that since USB is packet-based and such high speed, that filtering information on a tap-wire would be computationally impossible for a PIC. Even if computationally possible, writing the filter in program code would be like trying to write something to filter fiber connections.... possible, but....

Also, through connection analysis, we discovered first-hand that what comes across a tap-wire is just about everything on the bus except information that you're looking for.

I'll post a drawing and some complete code soon, but in the mean time, have a quick question. The USBN9604 has a microwire interface that we are trying to implement, instead of a parallel interface that is available. I have no experience programming for SPI, and am still new to PBP... but have coded quite a bit in MPASM. Attached is some rough code put together for this project. The code does no recording of keystrokes, it just takes one byte in from the USBN9604 and sends that byte out to the PIC USB connection.

The 9604 data sheet is here, which says that I have to send a read/write command before executing such read and writes. Also, it says, "1 cycle = 8 SK clocks. Data is transferred after the 8th SK of 1 cycle."

This is code that has been snipped from all over, then peppered with morsels fixing, then cut, replaced, and interrogated. I will not be able to test it on the PIC until tonight. But before that, can somebody take a look and critique?

What is the difference between hardware SPI and software SPI? I think my code might be a mix of both.... which probably will not work. In other words should I be observing SSPBUF for changes, or should I use an interrupt? Also, how do I tie the SPI interrupt to a particular pin? A solid code example or link to would be appreciated.

USBN9604 Data Sheet:
http://www.national.com/ds/US/USBN9604.pdf

Thanks all.

[kirtcathey]

Crazy question... but is microwire the same thing as SPI? Everything I have read tends to associate the two, but nothing clearly states that they are the same thing. Or, is microwire the same thing as I2C; or neither is related?

[Kamikaze47]

I believe SPI and Microwire are related yet not exactly the same, and I2C is different again.

http://www.scienceprog.com/microwire...o-spi-and-i2c/

[magestik]

SPI is a close cousin of the older Microwire.
I2C is quite a bit more complex than SPI and Microwire.

There is a minimum of 3 connections for SPI and Microwire: serial clock, serial data out and serial data in. Therefore you'll see those interfaces sometimes referred to as 3-wire interfaces.

If you want to connect N devices to your microcontroller with Microwire or SPI you need to sacrifice 3+N pins to do the job. This is an area where I2C has an advantage.

Microwire and SPI shine when it comes to speed. I2C was initially specified at a maximum speed of 100kbits/sec. This was later increased to 400kbits/sec and lately some devices started to show up that boast 1Mbits/sec. This still pales in comparison to Microwire and SPI speeds. SPI has the edge over Microwire, due to the availability of higher speed peripheral devices. Today's serial EEPROM for example support up to 3MBits/s for Microwire and up to 10Mbits/sec for SPI. But even the slowest Microwire and SPI peripherals still beat the typical 100 or 400kbit/s I2C speeds.

Here is also a comparision between several serial Protocols, including I²C, SPI and Microwire.

Hope this help.

[kirtcathey]

Well... I decided to go with an 18F4550, since it gives a little more room for evil expansion.

Here is a spaghetti schematic, so good luck trying to find the wire routes. Still trying to figure out some things on Eagle. Please take a look and comment. Am walking over to the breadboard in a few minutes to start putting it together.

Disregad X1 and X2. Those are just place holder sockets for extra SPI devices, like an MMC or bluetooth.

[magestik]

Didn't you forget to wire the data/adress bus ?

[kirtcathey]

I just changed the drawing in the attachment above. Moved the connect to clockout on the 9604 to the WR/SK pin. Is that correct? To have the same pin going to both SK and SDI on the PIC?

Data address bus.... can you elaborate? Got it! The eagle device is a bit funky.... confirmed the data sheet and will update the drawing.

Thanks alot.

[magestik]

D0/AD0 to D7/AD7 pins on the 9604, how does the two chip communicate ?

[kirtcathey]

The data sheet and the Eagle symbol confused me. Here is an update.