Reprogramming a Parallax ESC with SimonK Firmware

Hey there everyone! I’ve recently decided to try getting my old tricopter to fly after years of neglect. The last time it flew, it crash landed in Buffalo Springs Lake and never flew correctly again. I noticed that two of the ESCs would heat up much faster when idling, so set out to purchase replacements. I’m still waiting for said replacements to arrive from China, but I happened to be looking through the hobby section at Microcenter and found an ESC that might do the trick. I couldn’t find any documentation stating whether this Parallax controller would be able to accept the greatly improved SimonK firmware, so picked up a pair and decided to give it a try. I’ve been wanting to try this firmware on this rebuild since everyone reports greatly improved throttle response and better handling.

The ESC is packaged in a plastic clamshell and looks just like any other ESC. The price is also reasonable considering I’m able to source it locally. This is great news considering my track record flying aircrafts…

DSC_6838DSC_6795Listed on the box, the Parallax model number is: 750-90000-RT. After opening up the box I found “HW30A” listed on the ESC. I did some more digging and found that this controller is also known as an XXD 30A Motor Controller. It is typically sold on Chinese bargain sites such as DealExtreme and runs about $8.50 each. Looks like I didn’t pay too much for the controller! Here’s what it looks like after removing the shrink wrap.

DSC_6799DSC_6805Looking at the ICs on the board, the first thing I noticed was the Atmega 8. Excellent! This means that we should be able to load the SimonK firmware on the ESC! Now, to figure out which firmware file to load…

Digging some more, I noticed that there were two types of MOSFETs on the other side of the board. There are 3 x TPC8103 P-Channel MOSFETs and 2 x IRF7832Z N-Channel MOSFETs per phase. This means that I should be able to load the standard “tgy.hex” file onto the controllers without issue! Great!!

I mapped out the pins on the programming header and verified them using a multimeter. Then I went ahead and soldered some wires to the pads temporarily in order to program the Atmega 8 with the SimonK firmware. I still haven’t made a programming jig since it’s always been quicker for me to just solder the pins to the board than put the jig together!

DSC_6811DSC_6805_MarkedI loaded up LazyZero’s KK Flash Tool and attempted to program the board… Moment of truth… Success! The programming showed no errors and verified correctly, which means that the software should be ready to run!

I swapped out the motor wires for some which already had bullet connectors, hooked up a crashed motor I use for testing, and connected my bench supply to the controller. Everything looks good!

DSC_6815It looks like the SimonK firmware is playing nicely with the Parallax / XXD motor controller. This is great news for someone in a pinch since crashes can happen unexpectedly and it can sometime be weeks before you can source the parts necessary to recover.

I hope this helps someone trying to get these low-cost motor controllers working!