This is the circuit board which I made during my initial days of playing with microcontrollers. The microcontroller used in the circuit is 8051 (AT89s52). Here are the specs of the board:
1. Serial communication (RS232): DB9 connector is provided on board and MAX232 IC is used for converting TTL to RS232 logic levels.
2. LCD: 16 pin connector for 16×2 LCD.
3. In Circuit Programming: A 5 pin male connector (white connector in picture above) is provided for burning the hex file directly from the DB25 port of the PC. The connector exposes MISO, MOSI, GND, VCC and SCK from the board. I made a custom cable to connect the circuit to the DB25 port of the PC.
4. IO Pins: All 32 pins are available to use. With this circuit I connected Ultrasonic sensor (PING) which works on PWM mode.