Hardware

Hardware Description 12/08/00 EWJ

Overview:

The PIC16F877 is a Microprocessor based system, including input and output (I/O) interfaces, on a single integrated circuit. This type of device is called a Microcontroller.

The '877 device contains several features that are useful when using the device to control a process. Not all of the features of the '877 are available at the same time so when the device is used in an application such as the robot choices must be made as to what features are going to be in the overall design.

The robot (I/O) features:

Ports- Three 8 bit ports are available their functions are as follows:

The 8 bit port RB:

*Bit*	Description	Function	Available on expansion connector JP3
RB0	Spare Pushbutton Input	Low = button pressed	Yes (pin13)
RB1	Beeper Output	High = Beeper ON	No
RB2	Right Track Sensor	Low = White surface	No
RB3	Reserved to program '877	NOT A USER FUNCTION	No
RB4	Left Track Sensor	Low = White surface	No
RB5	Reserved LCD serial line	NOT A USER FUNCTION	No
RB6	Reserved to program '877	NOT A USER FUNCTION	No
RB7	Reserved to program '877	NOT A USER FUNCTION	No

The 8 bit port RC:

*Bit*	Description	Function	Available on expansion connector JP3
RC0	Spare	Advanced user I/O	Yes (pin 14)
RC1	Spare	Advanced user I/O	Yes (pin 16)
RC2	Spare	Advanced user I/O	Yes (pin 18)
RC3	Reserved D to A communication	NOT A USER FUNCTION	No
RC4	Spare	Advanced user I/O	Yes (pin 15)
RC5	Reserved D to A communication	NOT A USER FUNCTION	No
RC6	Reserved D to A communication	NOT A USER FUNCTION	No
RC7	Spare	Advanced user I/O	Yes (pin 17)

The 8 bit port RD:

*Bit*	Description	Function	Available on expansion connector JP3
RD0	LED D3 / Right Motor Reverse	High = D3 light ON and Right Motor Reverse	No
RD1	LED D5 / Right Motor Forward	High = D5 light ON and Right Motor Forward	No
RD2	LED D6 / Left Motor Forward	High = D6 light ON and Left Motor Forward	No
RD3	LED D4 / Left Motor Reverse	High = D4 light ON and Left Motor Reverse	No
RD4	LED D2	High = D2 light ON	No
RD5	LED D1	High = D1 light ON	No
RD6	LED D23	High = D23 light ON	No
RD7	LED D22	High = D22 light ON	No

Analog to Digital conversion- Eight inputs are provided to measure analog signals. They are converted in the '877 to a 10bit digital value. Your software can request this data.

*Channel*	Description	Available on expansion connector JP3
AN0	Left Front Sensor	No
AN1	Right Front Sensor	No
AN2	(Battery Voltage)/3.13	No
AN3	Spare analog	Yes (pin 2)
AN4	Spare analog	Yes (pin 6)
AN5	Spare analog	Yes (pin 8)
AN6	Spare analog	Yes (pin10)
AN7	Spare analog	Yes (pin 12)

Digital to Analog conversion- Two outputs are provided to control the speed of each motor. These outputs take a 10 bit digital word and convert it to an analog voltage.

Important links for understanding and utilizing the Robot circuitry:

Microchip PIC16F877 datasheet

Microchip MPLAB-ICD development system

Serial LCD: LCD display manual

D to A converter: Linear Technologies LTC1661

Motor Controller: BA6209

Schematics:

Page 1: Microcontroller circuitry

Page 2: IR sensors

Page 3: IR emitters

Page 4: Power and drive circuitry