EEVblog > EEVblog Specific

EEVblog #1144 - Padauk Programmer Reverse Engineering

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David looks at the pins on the Padauk PMS150 programmer for potential reverse engineering.

TLDR; It doesn't look easy to reverse engineer this protocol, it's messy with lots of voltage levels, as Padauk said it would be.
Just buy the programmer for now!
There is also a Flash/EEPROM re-programmable version of the chip, the PFS154C.

Looks like the first generation PIC16C54 programming levels, with fewer active IOs.  The old PICs used to use half the IOs to be programmed with wacko voltage transients and some analog levels thrown in as well.

Voltage levels on I/Os are probably not important, they are just matching the supply voltage, but it would probably work fine as long as you cross the threshold.

Just use a logic analyzer to grab their logical level. Clamp it with diodes if needed, although I suspect that simple current limiting resistors will be sufficient.

Regarding the different voltage levels: Old EPROMs required this, too. For example some algorithms verified if it was programmed correctly at 6V and 4V. So might be that the highest voltage phase is the programming phase, and two other low voltage phases are verify, and maybe a normal voltage phase for reading the ID etc.

Is anyone else a little confused by this?

Did I miss part of the video or something or did you not tell us how long the total programming time is? 
ms, seconds, tens of seconds?  That's kind of important to get an idea of the amount of data capture required.

Also did you intentionally grab the least capable data acquisition device possible?  We all know that lab is jam packed with high end gear that almost never gets used.  I'm pretty sure there are at least a couple multi-thousand-dollar deep memory 4 channel MSOs with real level triggering on the digital channels that should be more than capable.  I'm also pretty sure you can take the couple 4channel Keysight scopes sitting around, time correlate all the analog channels between scopes, and dump all that to a PC for a full time deep memory data dump.

It's one thing if you want to do some simple Arduino project video for beginners and don't want to scare viewers off by using test equipment they probably won't have.  It's another thing to do a real engineering project like reversing an uC programming procedure with only toy test equipment and then sound surprised when it didn't all just work out and you couldn't get all the data you needed.


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