JED Micro
Designers and manufacturers of audio/visual and industrial controllers in Australia

JED AVR256 Single Board Computer using the ATmega2560

AVR256 angle photo

The detailed specification of this card is downloadable as a pdf: AVR256 spec

A dimensioned drawing is available as a pdf: AVR256 dimensions

Layout drawing as a JPG file: Functions of AVR256.jpg

Port allocations and functions document pdf: AVR256 ports

Hi-res photo of AVR256 board: AVR256.jpg

CPU Data sheet: ATMega2560

JED AVR256 standard architecture for ATmega2560 applications

The ATmega2560 is a standard ATmega core CPU with 8K RAM, 256K FLASH, 4K of EEPROM and is in a 100 pin package. It has 4 serial UARTs, I2C and SPI interfaces, and 86 I/O lines. The full device data-sheet is 449 pages long, and is available at

The JED ATmega2560 board is an example of a CPU applications board for general use using this CPU, but differs dramatically from the usual board sold by microprocessor companies, in that all the inputs and outputs are industrial interfaces. This is an industrial-strength board, useable in real-world applications:

  • Sixteen “Analog” ports, which can also be digital inputs, eight with pin-change interrupts. (These can, for example,  handle 2-phase rotary position or shaft encoders very efficiently);
  • Sixteen other ports can be digital in or out. Four also have “input capture” for waveform capture/analysis, and four feed counter/timer inputs. Outputs can have up to seven Pulse Width Modulation outputs;
  • Output ports are 10 amp FETs with built-in high-energy protection and 60 volt flywheel clamp on the chip;
  • Back-to-back clamp diodes are placed on all user lines for ESD protection;
  • Series resistors for current and EMC limiting on all inputs;
  • Voltage divider resistor pairs for setting input thresholds and voltage ratios and full-scale ranges for all analog and digital inputs. Analog input is 10-bit resolution by up to 16 channels. Basic input range is 0 … 4.096 volts;
  • One additional port is a 1-Wire port for device expansion or operator certification/identification;
  • Four RS232 Serial ports have ESD protection and EMC filters;
  • Ultra-stable Real Time Clock with Temperature Compensated Crystal Oscillator (TXCO) for +/- 3.5 minutes/year max error. Clock device also has a 3 degree accuracy temperature sensor as board internal temperature readout;
  • SPI and I2C expansion ports to add-on upstairs boards to allow for more com ports, or high-resolution Delta-Sigma ADC (eg for Thermocouples or stain gauges for accurate load-weighing systems) or DAC (Analog output);
  • Optional text or graphic LCD display and keyboard interface;
  • Optional 2-axis digital accelerometer chip for shock detection;
  • All devices used are full industrial temperature range and board is designed for lead-free manufacture.

Flexible memory expansion is provided: CPU RAM can be expanded to 64 Kbyte, a 32Kbye non-volatile FRAM and a 8/16 Mbyte DataFlash provide non-volatile data logging memory, and an optional SD/MMC interface can provide many Mbytes of removable data logging memory. Optional host USB connection is available to “USB Memory Sticks”.

Com ports

The Standard configuration of serial ports is shown in the photo (above), where the four RS232 four black 10-pin IDC connectors can be seen across the top of the board. (This photo also shows the XPort device which is an option on Com 1.)

This photo also shows the four-pin connector(J29) loaded in place of the SD/MMC connector which adds three more input lines, including an external interrupt and T3/Int6.

Four serial ports with flexible loading of interfaces for the four CPU UARTs is provided, so as well as RS232 on all four ports, options allow for:

  • USB slave port for communication to a PC (serial port emulation in the PC;
  • USB host port, to communicate with memory sticks;
  • uBlox LEA-4H or -4S GPS for high sensitivity, low current (38mA) positioning, able to accept DGPS corrections;
  • 802.11 or other radio (eg 433Mhz or Zigbee) or interfaces to cellular phone networks or phone line modems;
  • X-port for 10/100 Ethernet interface for networking or web page hosting on-board the AVR256;
  • RS485 networking from the AVR256 to interface to off-board local data gathering/control networks.
  • These facilities make the AVR256 board ideal for asset, vehicle or mobile machinery monitoring and tracking.

Flexible power control compatible with 12 volt vehicle or solar powered and battery powered systems is provided, allowing systems to auto-start from a real-time-clock alarm, or from an external event such as an ignition turn-on in a vehicle. (Customised versions of this board could have protection and switching regulators for 24 volt vehicle environments.) Communication devices and ports can be powered up and down under program control.