Posted by: freesystem | March 1, 2008

ATmega2561 Development Board Schematics

Motor Driver and Xbee Module

I have been working on a development board for the ATmega2561, mainly because this chip has so many features and I could not find a board with it. The board is more of a breakout board then a real development board, because it has very few peripherals built in. It does has a 7805 voltage regulator, a Max232 UART level shifter(for both USARTs) and an ISP Header. The rest of the pins are broken out to headers, each one getting its own +5 and Ground pin, in servo pinout. I figure any other stuff I need on it I can build a separate board for, making this one of the most flexible AVR platforms out there. I have already designed a Motor Driver and a Maxstream Xbee wireless(see pic above) module for it.

The motor driver communicates over serial to an on board ATmega32, which drives the motors. This takes the overhead of driving the motors off of the main CPU and opens up more PWM pins for other uses. The motor driver has six(thats right, you heard six) LMD18200 3 Amp motor drivers with current sense and thermal flag. That means that you can drive six motors, 3 bipolar steppers, or one 18 amp motor. The driver board also had a thermal flag output through an eight input NAND gate, so if one or more of the drivers is overheating the main processor will know. Also hooked up to this pin is a fan driver through a MOSFET, so you can make it turn a fan on when one starts overheating, or override it through the override pin. It also has an ISP header for firmware updates, and serial for communication with the main processor.

The Xbee module isn’t quite as amazing as the motor driver, but it does have some cool features. It has a triple interface system, meaning you can interface it to a robot over USART, a robot or computer over level shifted RS-232, or a computer over USB. It will support a Xbee or Xbee pro, and breaks out every pin on them for further hacking. It also boasts an on board voltage regulator, and transmit/receive LEDs.

Finally, the main board. I already talked a little about the board, so ill focus on the chip itself. It has 256Kb of Flash, 4Kb of EEPROM, and 8Kb of SRAM. It has six timers with a nine channel pulse width modulator. Also, a 10 bit ADC with 8 channels. See here for more information.

I will be posting the final schematics later today. They will be posted under the GPL License.


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