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PIC18F8520 (10/40MHz) Processor with PWM, H-Bridge, SD/MMC Socket, EEPROM, LCD Interface, RS-232, RS-485 Multi-Drop, and Battery Backed Real-Time Clock

This module is a versatile high-power development platform for your next prototype or project.  8V-24V AC or DC from a wall transformer is rectified and filtered then distributed through Poly-Fuse auto-reset fuses. Separate regulators for PIC Processor, Sensor Inputs, Control Outputs, and H-Bridge Driver.

The PIC Processor is powered from 5V, and has both 10MHz and 32.768KHz Crystals attached. The 10MHz Crystal can be operated at 1:1 (for 10MHz CPU), or 4:1 PLL (for 40MHz CPU). In addition, the 32.768KHz Crystal allows the PIC Processor to enter a sleep-mode and can be woken up by an interrupt. This enables a very low power consumption.

The PIC Processor is programmed and debugged using a 6 pin 2MM header. This header enables a Microchip ICD-2 debugger/emulator to be connected to allow ICE (In Circuit Emulation) and programming.

The PIC Processor has both RS-232 (P7) AND RS-485 Ports (P8 & P19) available. The RS-232 port connects to the Serial Port of the PIC Processor so an attached PC or other serial device can communicate. The RS-485 port is configured as a multi-drop LAN, with a port bit enabling the TX function. This allows a multi-drop LAN to be setup. Both Serial Ports are accessible through 6pin RJ-11 Modular Jacks.

Three PWM outputs are connected to the PIC Processor. The first drives a P-Channel MOSFET to control and generate a source voltage used for the Open Collector Switch Outputs. By using the PWM and MOSFET, any voltage can be generated and dynamically adjusted or even user configurable. The Current and the Voltage of the Switch Output Source is monitored by analog inputs to the PIC Processor. Since the Voltage can exceed the 5VDC supply of the PIC, a voltage divider network is employed to scale the voltage measurements so they remain within a safe range.

The other 2 PWM outputs are connected to the H-Bridge driver. One is normally configured as a 'direction' control, but for flexibility, any configuration can be enabled with software. The Current consumption of the H-Bridge section is monitored and fed into an analog input pin of the PIC Processor.

Open Collector "Switch Outputs" are presented on a combination 12 position terminal strip and pin header as well as two 6pin RJ-11 Modular Jacks. These outputs are connected to an 8-bit port of the PIC Processor, and are individually controllable. Eight status LED's show the current state of each separate ouput.

Diode Clamped "Sensor Inputs" are presented on a combination 12 position terminal strip and pin header as well as four 6pin RJ-11 Modular Jacks.  These inputs are conned to an 8-bit port of the PIC Processor, and are individually readable. Eight status LED's show the current state of each separate input.

An SD/MMC Memory Card Connector is attached to GPIO pins of the PIC Processor. In SD Mode, there is only a singe data I/O bit to the card, where in SD mode, there are four data I/O bits. Both modes are supported, as well as the Card-Detect and Write-Protect switched of the card socket. Additional software is required to operate the SD/MMC memory Card Connector as there are FLASH file system implications to implementing this port.

Real Time Clock (RTC) functions are provided by a ST M41T80 Clock Chip, CR2032 Batter, and a 32.768KHz Crystal. The Batter is inserted into a battery-holder from the back of the module, and is fully field-replaceable. The RTC reference pins are brought out to a 3pin header (P18) so that the reference frequency can be measured.

Non-Volatile Storage (NOVRAM) in the form of an EEPROM from Atmel (AT24C02) is socketed and can be replaced with any suitable I2C controlled EEPROM. The NOVRAM and RTC are the only I2C device on-board, but the I2C bus is also available on a 4pin header (P12) which includes VCC and GND.

LCD Displays can be connector via 2 separate ports. A really nice Graphics LCD can be attached to P4 which is a .5MM flex-circuit connector (see sample picture). This LCD is a pixel-based graphics display, so any character or image or symbol can be displayed. We can supply sample code for a 5x8 font and the necessary driver to control the LCD. Alternatively, a character-based LCD using the 'standard' parallel interface can be connected to P10.

For Keyboard connection, P9 supplies 8 bits of I/O which can be configured as a row/column scan keypad matrix.

We supply this module with the PIC with code loaded that will 'walk' the LED's and display voltages on the Graphics LCD, which is our QC final test. Source will be supplied, but some of the driver modules may be supplied as linkable libraries due to licensing restrictions.

We can also supply a bare-board only, if you have the desire to assemble these things. The passive components are 0603, and are quite small, so be prepared!

Board Dimensions: 6.0" X 10.0"

Full Schematics and Data Sheets are supplied, with sample code written using the Microchip C Compiler.

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