Controller module

Main module of a HomeLab is a controller development board (controller board) equipped with AVR ATmega128 micrcontroller. The board consists of in addition to microcontroller several peripherals, voltage stabilizer, connectors etc. The controller board has the following features:

• Atmega128-16AU microcontroller in the TQFP64 package (ROHS)
  • 8-channel 10-bit A/D converter
  • 128kB Flash memory (program memory)
  • 4kB EEPROM memory (data memory)
  • 6 channel programmable PWM
• Standard 6-pin In system programming interface (ISP) connector
• 16MHz clock (can be changed very easy, crystal is mounted on small 2-pin socket)
• Real Time clock (RTC)
• Reset protection circuitry for the ATmega128
• Status LED and Power LED
• Standard DB-9 serial port connector with RS232 transmitter / receiver
• All Atmega signals available on three connectors (1. D, B, E ports, 2. G, C, A ports, 3. F port with ADC I/O lines)
• Reset button
• JTAG 10-pin Interface connector
• 2-pin on/of connector – can be used for connecting on/off button
• DC 2.1mm power connector
• Built-in voltage stabilizer

Controller module

Module is equipped with AC/DC rectifier circuit and LDO voltage stabilizer (with low dropout) - external feeder with voltage stabilization is not needed.

Module can be powered just from step down transformer with output voltage greater than 6 Volts and lower than 15 Volts. Module has wrong-polarization protection circuit (Greatz bridge). POWER LED is signalizing connected feed (“POWER” description on the board).

Circuit can be equipped with external power switch by connecting it to S2 2-pin on/off connector. If external power switch is not used, S2 2-pin on/off connector must be shorted.

All ATmega128 signals are available on three connectors on the edge of the board. Connectors pin assignment is described in next part of this instruction. It includes full descriptions of ATmega128 pins and their alternative functions. The module is equipped with microprocessor reset circuit (when power on) and reset button for microprocessor restart. Microprocessor can be programmed with ISP or JTAG programmer.

To the seventh pin of port B (named as PB7) is connected to the status LED (described as PB7 on the board). This LED can be used as a status indicator of application software. Low state on PB7 pin causes that the status LED is lighting.

Module provides two serial ports described on the board as UART1 and UART2. The first one is 9-pin female connector (DB-9 PC serial port compatible) and the second is 3-pin connector. Required signal conversion to serial standard provides MAX232 circuit.

Multiplexer 74HC4053 provides full use of ports, also these that are used for microprocessor programming, because when the processor is in reset state (when programmed) multiplexer witches PE0, PE1 and PB1 signals to ISP and JTAG connector. When processor is in run state these signals are switched to connectors on the edge of the board.

Module is equipped with external memory (Atmel AT45DB041B). It is 4Mbit serial data flash memory connected to Master/Slave SPI serial interface of the microprocessor. Internal Real Time Clock is connected to external 32.768 kHz crystal resonator named as X2 on the board.

When connecting the controller module with other peripheral modules and devices, the last thing is connecting the power supply. If power is on, it is dangerous to connect and disconnect external devices. Modules have to be connected with each other with great care without applying strong force as this can bend connectors. JTAG-ICE programmer have to be connected to the correct port and the ribbon cable directs out from board (red stripe is by the power supply connector side).