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Bus Pirate Development / Poor Port Protectionb
I'm very interested about buying and use the bus pirate, but before that, I was analyzing a bit the electrical schematic. Well, in my 3 years of electrical engineering experience, I learned one stuff "unprotected IOs gets burned - ALWAYS", soo I saw that there is no protection from the uC to the target connector, even 47R series resistor and a diode clamp, nothing!
Take a look about the bus pirate schematic.
There is no protection, working with development, is very very common to get the IOs in short-circuit, or to vdd, gnd or any unexpected situation.
This will damage the PIC easily.
I designed this interface before know the pirate bus (for my old company), the target protection hardware was designed for easy maintenance and to be resistent for the lab and to field..
Also, this hardware is compatible with 3v3 and 5v systems as you can change the pull-up voltage and pull-up individualy two lines (sda and scl ), diode clamp protection, high voltage reversed power and short circuit, about every thing that can happen in the development enviroment.
I realy would like to suggest this schematic as a hardware improvement for the bus pirate project, only few resistors, capacitors, two 74126 chips, and few fets transistors.
If you think is too much, take a look into the Renesas E8 debugger and the Microchip ICD2 debugger, they all uses this protection ( or part of ) and there are no problems with extras capacitantes or delays.
here, the schematic.
http://rapidshare.com/files/348875667/U ... e.pdf.html
Best regards!