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New web site links: Home/Contact > Single Board Computers > AVR256

JED AVR256 / 257 Single Board Computers using the ATmega2560/1 CPU

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

Drawing below as a JPG file: Functions of AVR256.jpg

Port allocations and functions document pdf: AVR256 ports

Hi-res photo of AVR256 board: AVR256.jpg

The AVR257 board is also available as a cut-down version of the AVR256. This version has essentially the same CPU but with 16 I/O lines only, two serial ports and the option of RS232/RS485 or the MMC card interface. It mounts in the same Hammond case 155.5 cm by 9.3 cm by 3.5cm as the PROM programmer and the J994 Midi interface (see Photo.) 

This unit is very customisable at load time, and is intended as a lower cost, cased version of the AVR256. Call Ed on (03) 9762 3588 if you have a need for such a configuration.

AVR256 functions

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 (right), 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.

This “Standard Architecture AVR256 board” allows a list of I/O devices to be interfaced consistently across many projects. The standard board layout is useable directly in many cases where no custom pcb size or mountings is called for. However, if customers need a particularly compact design, the track-work on the pcb can be re-laid out, with maybe some different external interfaces (eg relays or opto-isolators or amplifiers) and connectors. If the port addresses are preserved in the re-layout, then the drivers will run unaltered on the custom board, but software development can start within minutes of powering up this standard board and then transferred to the customised or “cut-down” version.

JED Microprocessors Pty Ltd.
173 Boronia Rd Boronia 3155, Vic, Australia. Phone: +61 (03) 9762 3588 Fax: +61 (03) 9762 5499.

Email for orders or technical queries:

AVR-ISP mkII, In-System Programmer for all AVR microprocessors, in stock, $A75 + GST

The AVR In-System Programmer is used for field upgrades of existing products using the Atmel AVR Architecture. The In-System Programmer is based on the STK500 Hardware and Software. It supports all in-System Programmable AVR devices. It is supported by all AVR compilers (CodeVision, Imagecraft C, BASCOM, AVR Studio). Because it runs from the PC USB port, it avoids problems with printer port modes (ECC, Std, etc) and operates under all PC operating systems with USB support.

It is supplied with a 6-pin programming cable, so is suitable for all the recent JED boards and modules shown above.

(Because a 10-pin cable header is not provided, there is a problem in interfacing to older boards with the 10 pin ISP header, or boards like the JED 585, which has a 14-pin conn ector, formed by adding 4 extra pins to the Atmel 10-pin standard. We are quite unhappy that Atmel has dropped the 10-pin support without any warning, and will soon make available an adapter board to convert the 6-pin cable to the 10 and 14 pin standards. Contact JED for availability.

A full data sheet is available for download at: AVR-ISP mkII user guide

Note: The older serial RS232 port AVR-ISP is no longer available. It has been suddenly deleted, without warning by Atmel.


AVR assistance from JED

If you are interested in using AVR processors for any project, small or large ... email or call Ed Schoell at with your comments or questions. (03 9762 3588)

JED offers a design service for boards or systems based on AVR, Xilinx gate arrays and a range of other electronic hardware and software projects. We have a group of standard circuit and gate array design modules, with matching software drivers developed during our time creating the Little Blue Computer and friends and we have designed a number of custom systems based on AVR using this experience. 

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(Updated November 26th 2008)