Don't actually know for sure that it's a zener but what would a normal reverse biased diode be doing in that part of the circuit? As for the function, I'll tell you when I've done my writeup
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The zener isn't in series with R4 so it's not helping with the regulation but that could be done by the external pullups so R4 remains a mystery. If you keep PIN2 in mind it's connected to the circuit without a voltage clamp so obviously the voltage required is readily available, why the zener on PIN1 then?
Well I know the circuit works since I use the dongle every day, figured the same after thinking about R1 for a bit. I suspect R4 is to overcome the zener capacitance and prevent it from holding the clock line high longer than desired, agree/disagree?
Haven't dumped it yet but that's why I put it in the Bus Pirate forum
Was bored today so I opened a dongle I had laying around, I've attached a pic and a circuit diagram I drew up for it. It only contains an I2C eeprom and a couple of passives but it's pretty smart, it uses a diode and capacitor to power the eeprom from the eeprom clock line.
Anyway, anyone have an idea what the resistors R1 and R4 are for? I'm assuming PIN1 and PIN2 are connected to Vcc through external resistors and are connected as SDA and SCL for normal I2C operation.
IR receivers are designed to filter out ambient light, that's why a switching carrier is needed, ie, a 100% duty cycle signal will be filtered out as well, any other duty cycle should work though.
Was thinking a voltage regulator to just give something stable from a supply up to about 9v, could use a big eeprom to store raw codes like some of the codes in the tvbgone library, with a big one we could store the entire tvbgone db which would be awesome. This project can easily become what the unzap failed at.
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I was hoping to be able to use it to capture raw IR signals and save them to fiddle with later, dump them to the pc via usb for example. Maybe generate some similar codes, store them and go try them on the device you got the originals from.
I'm using a basic LIRC serial receiver but I'm looking for a usb unit with a transmitter as well, anyone come across anything like this? (Has to work with LIRC)
I didn't think a drill press would make that big of a difference but boy was I wrong. I use to use a dremel for drilling pcb holes and it worked fairly well but I did lose a pad every now and again.
Getting a new drill was partly why I tried making this board, it's pretty big and not cheap considering I'm using it only for pcb drilling but works real well, I've tried drilling holes down to 0.4mm with no problems.
I wanted to test out my new setup so I tried to create a home made bus pirate pcb, all in all the results were pretty good, the board came out real well and drilling didn't give me any problems, the small vias tend to be a bit weak so spraying over a protective coating is pretty important.
To do the through hole plating I use small wires if I can afford a bump on the board where I soldered it or fill it with a conductive paint, if using conductive paint you can simply put some sticky tape over the board before drilling to prevent the paint from going anywhere unintended.
I've made some pretty stupid mistakes in the past with my layouts so I prefer making a cheap prototype first, what do you guys prefer, going cheap or doing a professional prototype run?
[EDIT]
Oh, I did a single layer board because I overexposed the first attempt which was double layer, the results are near perfect with double layer since alignment when using photo resist is pretty good.
