Update: 19 September 2012:

Hobbyking now stocks the excellent Atmel Atmega Socket Firmware Flashing Tool. Combined with the USBasp AVR programmer flashing any Atmega based ESC is now much easier. No soldering required, simply cut away the heat shrink over the MCU put the tool over it and flash.

SimonK ESC firmware flashing HK Blue Series 20A and HK F20A

For those seriously into quads you would have heard of SimonK and his firmware for Atmega based ESCs. I am going to focus on flashing a HK Blue Series 20A ESC. These are popular so if you cannot get hold of one the Mystery Blue 20A is pretty much the same unit. Another very good ESC for flashing is the  HobbyKing F-20A. You have to build your own flashing adapter, but once you have that they are much easier. I will cover that here also.

Here they are side by side:




The Blue series is smaller and lighter, but I like the F20-A better as it cheaper and has longer leads. Also if you mount it right is much easier to re-flash once it is fitted on your quad.

Difficulty: medium.

Hardware required.

• USBasp programmer.
• HK Blue Series 20A
• or Mystery Blue 20A
• or HobbyKing F-20A
• 6 very small screws.
• Soldering iron.
• 2 servo extension leads.
  

Step 1: Install your USBasp drivers.

No drivers are needed for Linux or OSX.

Windows get your drivers from here you have to manually install the drivers. Josh on Flite Test shows how to install the drivers on Windows 7, and also how to use KKMultiTool on a HK controller board. Worth a look.

Step 2: Programmer to ESC connections.

Here is the business side of a blue series with the programming pads labeled. Do not cut your cover off like I have here, as you will see there is no need.

Just a small strip of the covering cut off at the corner of the pcb near the red motor wire.
With a sharp hobby knife make a small incision first and then lift from underneath to cut it. This way you wont cut any tracks.


I made this for the F20-A with headers that were cut out of an old circuit board. The pins were bent inwards to fit and then ground flat with the face of a Dremel cutter. I simply hold it in place while programming. You could also attach a peg to this setup but I am already in too much trouble with the missus.

I made it into a permanent fixture on my programmer by attaching it to the seldom used 10pin header. The solid cores of stripped network wires are pushed in and held with hot glue.

That is the F20-A setup ready. Back to the blue series:

Prepare our leads. I used the female ends of two servo extension wires. You will have to cut off the outer plastic.


I find it easier to slide the pins out before I solder them on.


Next you will need four very small and relatively long screws. Most people should have a few dead servos lying about. These were from my Esky Belt heli.


What are looking for is a pointed and threaded end. If they are not pointed it will just make it a bit more difficult but not impossible.


Here I have my favorite pointy tool which is a stainless steel dental tool. Any sharp pin held with pliers will do the same job.


Obviously we want the hole right over the pad.


Next get some solder on your screws, you do not want the screws getting too hot while they are stuck in the heat shrink.

These three you can offset the holes a little to avoid shorts.


Apologies for the dirty nails. These two are tricky because the heat shrink is much closer to the board, lifting it with a screwdriver helps.
Once they are all in, we can solder our wires on then match them up with the right connections on the programmer.

sudo apt-get install avra
sudo apt-get install avrdude
make
sudo avrdude -c usbasp -p m8 -U flash:w:bs_nfet.hex

On windows you might be able to install avra under cygwin or such, however I am going to use avrasm2 which is a little easier to install. In fact it is just one standalone executable, no installer, no dlls.

Unfortunately you cannot simply download avrasm2 from Atmel. In their wisdom it only comes with the monstrous (1 gig installed) AVR Studio and at that buried way down in some obscure directory. Being such a great guy, I have made a nice zip file with avrasm2.exe in it. I can even do this legally as long as I include the license file with it.

Usually avrasm2 also comes with a bunch of include files for all the processors, so if you are going to get into assembler you will need to track them down. SimonK has the relevant include file included with his source so all you need here is avrasm2.exe.
 
Copy avrasm2.exe to a directory somewhere and then execute it from the command line. You should see something like this:

AVRASM: AVR macro assembler 2.1.51 (build 39 May  4 2012 15:31:44)
Copyright (C) 1995-2012 ATMEL Corporation

Along with a couple of lines about usage and accessing help.

I run avrasm2 under wine on osx. I installed wine using macports. I also found a nice little shell script so I can run avrasm2 from the command line just like you would in windows. For those interested here is the shell script.

#!/bin/bash
wine ~/avrassembler/avrasm2.exe -I ~/avrassembler/include -fI $1 $2 $3 $4 $5

Send me an email and I will add detailed instructions for the mac users.

Install AVRDude

.gitignore is used by github where the code is stored.
Makefile is a script that compiles all the binaries at once. We are only interested in one type of ESC at a time so I am not going to cover it here.
README.md read it! Its got lots of information and instructions on calibrating your ESC once flashed.
The inc files are for each of the different types of ESCs. We will be using bs_nfet.inc
tgy.asm. This is the main source file and here we will make some changes. Open it up with any text editor.