Difference between revisions of "PIC Microcontrollers with C18 Compiler"
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==PIC Microcontroller== |
==PIC Microcontroller== |
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The microcontroller used for this project is the PIC18F4431 made by [http://www.microchip.com Microchip]. This is an 8-bit microcontroller with motor PWM generators, a quadrature encoder interface (QEI), and other "peripherals". The microcontroller uses an external 40MHz oscillator. |
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The microcontroller controls two wheel motors with PWM driving external H-bridges. The H-bridges draw their power directly from the batteries, not regulated power. |
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Each of the wheels also has a quadrature encoder. The left wheel encoder is connected to the PIC's QEI via a schmitt trigger buffer. The right wheel encoder is wired to a U.S. Digital LS7183 chip (because the PIC only has 1 QEI) which outputs pulses on one of two pins, depending on whether the wheel is spinning backwards or forwards. The two pins are then each connected to a counter on the PIC, which keeps track of the number of pulses. The location of the wheel can be determined by subtracting the reverse-pulse counter from the forward-pulse counter. |
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The PIC is interfaced with the XBee modem via the RS-232 serial interface. |
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==Programming the PIC== |
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==XBee== |
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==Code== |
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==PCB== |
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Revision as of 18:19, 5 July 2007
PIC Microcontroller
The microcontroller used for this project is the PIC18F4431 made by Microchip. This is an 8-bit microcontroller with motor PWM generators, a quadrature encoder interface (QEI), and other "peripherals". The microcontroller uses an external 40MHz oscillator.
The microcontroller controls two wheel motors with PWM driving external H-bridges. The H-bridges draw their power directly from the batteries, not regulated power.
Each of the wheels also has a quadrature encoder. The left wheel encoder is connected to the PIC's QEI via a schmitt trigger buffer. The right wheel encoder is wired to a U.S. Digital LS7183 chip (because the PIC only has 1 QEI) which outputs pulses on one of two pins, depending on whether the wheel is spinning backwards or forwards. The two pins are then each connected to a counter on the PIC, which keeps track of the number of pulses. The location of the wheel can be determined by subtracting the reverse-pulse counter from the forward-pulse counter.
The PIC is interfaced with the XBee modem via the RS-232 serial interface.
