Cheap and good ESC for Tricopter

ESCs are needed for every multirotor. Some are cheap, but dedicated to planes (slower response), some have extra features in firmware, but costs a little more.

But thanks to SimonK and his firmware, there is possibility to reprogram many of them. So, to build my Tricopter I decided to buy cheapest one available and reprogram it:
HobbyKing SS Series 15-18A ESC

So, let’s modify it 🙂

Hardware

In order to download new firmware you need some Atmel programmer (I use USBasp from HobbyKing but on eBay you should get better and cheaper version supporing both 3.3V and 5V logic levels). Also you need some real soldering skills, steady hand and possibly magnifying glass 🙂

At start: remove shrink-wrap from ESC. The best and safest place to cut it is on one side.

After getting shrink-wrap off, first surprise: I have probably new version of pcb because it looks a little different than on pictures from list of supported ESCs. But luckily it’s almost the same but with added programming pads:

As you can see on above picture there are 6 pads. But bad news is that some are clean and flat, and other one are with ‘balls’ of tin (and on each ESC there were different combination of these). This makes difficult to make some programming connector to touch reliable to these pads.
So, only soldering left for me.
To solder without problems to such small pads I made ‘balls’ of tin on all pads:

Then I soldered header pin connector with very thin wires (Kynar wires, diameter 0.2mm/AWG32). If you first tin end of this wire, then soldering it to the ‘balls’ on pcb is easy (with magnifying glass 🙂 ).

And just connect it to USBasp and program it!

Software

Of course you need software to flash it into ESC 🙂

Getting it

I got it directly using:

Then I modified tgy.asm to disable runtime calibration:

In my opinion this is not needed for this ESC as it has quartz oscilator and will be controlled by MultiWii board instead of receiver.

Code compilation

If you don’t want or you are unable to compile this code, firmware compiled by me is here.

Programming firmware

In this step you need Avrdude or other AVR programming software which allows to flash ready firmware in Intel Hex format.

Bootloader

Above code contains a bootloader, so further reprogramming could be very easy and could be done using only BEC/PPM connector. But for such programming you will need another device: Turnigy USB Linker or you could do it yourself using Arduino board and ArduinoUSBLinker software.

In order to bootloader works, it’s needed to change BOOTSZ and BOOTRST bits, so new value of hfuse should be 0xca (or 0xc2 if eeprom should survive chip erase).

Testing

I recommend to connect ESC to battery first time using 10 Ohm resistor (few Watts recommended). It’s value is small enough to allow motor start and run, but it’s also large enough that any software or hardware malfunction couldn’t burn your ESC.

And on the end – small video with original and flashed ESCs with motors: