Look what came out of my reflow oven!

Hi guys,

Here I want to show you my new autopilot hardware which I worked on the past weeks.

The layout and the connections of the boards are chosen for my own convenience.

So airspeed sensor, receiver input, GPS, LEDs and I2C connections are at the front of the autopilot.

Servo output, serial ports, ADC and open drain outputs are at the back.

I also belief in the modularity, having two boards it is easy to replace the main board in the future when I need more performance and using the "expensive" IMU board again. It's still a small system with a height of 12mm and board dimensions of 62mm x 40mm, the weight is 35grams (mainly due to the stiff 1.6mm thick boards).

It's almost APM code compatible, only difference is the gyro+acc. sensor connected directly via SPI and the airspeed sensor which is connected to I2C via a one channel 16bit ADC.

It has all sensor "needed" on the IMU board, which are:

Compass: HMC5883L

3 axis Gyro+Acc.: SD746 (or MPU6000 if it is coming available and prove to be better that the SD746)

Baro: BMP085

Airspeed: MPXV7002 (via ADS1100 16bit ADC)

Three open drain outputs

Three ADC inputs

Three Serial ports

I2C port (5volt)

GPS (Serial port, EM406 pinout)

Status LEDs

Main board:

ATmega2560

ATmega328

TRACO regulator (max 36 volt input to 5volt output)

Eight channel receiver input at the front of the board

Ten channel servo output at the back of the board

Below are some picture of my work, now I have to test and do......some more testing :-)

Please let me know what you think of this solution......

Wish you all the best,

Alexander

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Comments

Alexander September 17, 2011 at 2:39pm

farooq, that is exactly what i had in mint. I have a Octo with mikrokopter electronics that I want to replace with this autopilot in the future. So having two extra servo outputs is always useful...but first is the axn floater that will get this board between the receiver and the servos :-)
Andre Lochner September 17, 2011 at 2:30pm

Very nicely done ! How easy was it to source components ? I live in SA and here it is extremely difficult to source components unless you order large quantities, and you have to wait a long time.
Farooq Niaz September 17, 2011 at 2:12pm

8 + 2 Servo outputs means we can have octo with camera Stabiliztion ?
Alexander September 17, 2011 at 2:10pm

Patrick, thanks for the compliment, indeed there is no USB converter on my boards, i did this on purpose. Now i can use this uart for ohter things like for instance osd. And THE other big reasion is that i didn't want to have stuff on my boards that are not being used during flight but can bring a risc of failor during flight.
For me connecting a ftdi cable with jst connector to the board is the Same as connecting a USB plug directly.
Your right on the 8bit mcu, this is why i can easily swap the main board in the future for a higher performance board
Patrick L September 17, 2011 at 11:14am

Well done, a nice and clean layout. The SD746 seems interesting with 16-bit conversion, configurable scale and bandwidth for gyro and accels. There's no USB connection so the uploads are via a serial port, I assume.

But you may want to update the main board sooner rather than later to an 100MHz+ 32-bit ARM processor (Cortex-M3 and beyond). The 8-bit ATMega is becoming a bit, well, outdated.
Amilcar Lucas September 17, 2011 at 9:39am

OK, now I've looked more carefully and I see that there are two different boards on the picture. For some reason I assumed it was the top/bottom of the same board.

Sorry for the silly question.
Alexander September 17, 2011 at 9:36am

Amilcar, it's a two board solution like APM+oilpan IMU board.

Only my the IMU board contains more sensors like compass and airspeed etc.
Amilcar Lucas September 17, 2011 at 9:25am

Sorry, I do not get it. Do you need the IMU expansion board or not ?

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