Saturday, August 20, 2011

The 0.01 Beta Application

This is the first version. It supports rate mode and Heading Hold mode. It´s working quite well but we have to adjust better the PID parameters. I did the tests with a HBKing II with a 450 tail on a "lazy susan". Now I'm waiting for a bluetooth device to connect it to the gyro so I will be able to send data to the PC in real time without cables connected to the Heli. My radio is a Spektrum Dx6i and currently I have 25% for rate mode and 62% for HH mode.
Later I will explain better the code...

Download and try it!

Here is a version for debug. The gain is fixed in the code so you can keep the gain connector connected to you PC and sending debug information like sensor values to the TeraTerm.

Download and debug it!

Compile and Load the Application

In order to compile the application you need to install the WinAvr.
Once you have the .hex file you can load it on
the gyro with the AVRprog tool (V1.37) and this hardware connected between the gain connector and a device that provides rx/tx TTL (5V) levels from your PC. You can find devices for USB or Serial port on Ebay.

(If your Tx level is 3.3V skip the R2 resistor)

Run a terminal program like TeraTerm baud 19200 8N1. Power the gyro (gain connector), the red led will flash, send an ESC key and the red led will go solid.

Close the TeraTerm and run the AVRprog, select the .hex file and program the flash.

Power down the gyro or send an 'E' with Teraterm and that's all! You have your application ready to run!

After power on the gyro will stay ~4 seconds in the bootloader red led flashing waiting for an ESC then the Application will run!

My stuff:

Thursday, August 18, 2011

Load the BootLoader

The goal is to load the application and configuration through the gain connector without any hardware mods. For that you need to program the a ATmega8 with a BootLoader to be able to communicate by a single wire (the signal wire on the gain connector).
I´ve used the DL5NEG bootloader slightly modified for this purpose.

Download the bootloader code and the hex file.

To program the ATmega8 you need a progr
ammer device like the AVRISP mkII or use the PonyProg and the PC parallel port with some extra hardware.
Open the gyro and connect the programmer
to the SPI interface (VCC, GND, MOSI, MISO, RESET and SCK) . See the pcb pictures and use your iron solder carefully.
Once the bootloader is programmed set the fuse bits like this:

Now you can remove all the wires that you have soldered and close the gyro!

The GA250 Gyro Hardware

Inside the GA250 you can find an ATmega8 and a mems sensor ISZ-650 from InvenSense.
Take a look on the OlliW's site for pcb details and schematics.

This gyro is made by ASSAN. You can buy it from HobbyKing.