PICARD80 Prototyping Board User's Manual. (R. CORDESSES F2DC January 2011)

Introduction. This new card, called PICARD80, is designed to ease the development of a prototype based on a 28 pins Microchip PIC microcontroller. Its mains characteristics are presented below. - Many PICs have Analog to Digital converters inside the chip but most are missing any Digital to Analog function. This new card was designed to fix this drawback and includes a Microchip MCP4822 dual channel 12 bits D/A connected to the PIC via SPI lines. Output low-pass filtering is provided on the card. If not used, the D/A converter can be unselected by proper settings of 3 jumpers. - RS232 MAX232A interface : this function can be selected or not by settings of 2 jumpers. - PIC ports A, B and C I/O pins available for connection to the external world by 5.08 mm terminal blocks on the edges of the card. - ICSP connector for easy programing with Microchip ICD/PICKit3 interface or compatible programmers. - Crystal or ceramic resonator can be used for clock generation. - Power supply : PCB footprints provided for either TO220 (7805) or TO252 SMD (LM1117) voltage regulators. Caution : install only one regulator on your PCB, according to the package selected ! - Foolproof power supply diode (Schottky or regular). - A LED can be connected to RA5 via a jumper (useful when debugging). - This card uses SMD 0805 and through-holes components. - Size : 86 x 74 mm (3.4” x 2.9") with 4 mounting holes in the corners. 1. Construction.

PICARD80 with a TO220 regulator

With a TO252 SMD regulator

The PCB is a 2 sides one and can be etched using the PCB artworks available from my Web site : http://roland.cordesses.free.fr/pic_card.html. You can also order it from FAR CIRCUITS (http://www.farcircuits.net/). A part list is included in Appendix 1 at the end of this document. - I suggest you solder first the SMD parts on the solder side, beginning with these near the center of the card and then going toward these located near the edges (see Appendix 2 for parts layout). - Install the 3 DIP sockets, the remaining through-holes parts ( R, C, L1, LED1, D1 and the crystal Q1) on the components side. - Some parts leads are used to connect GND tracks on the solder side to the top side ground plane as shown in the Appendix 3. - Don't forget to solder small wires between the ends of tracks 1 and 2 on both sides if your PCB is not through-hole plated : Appendix 3 shows where they are located. - Solder a 6 pins single-row male connector at JP7 (ICSP interface). - SPI signals going to the DAC are selected via jumpers JP3, JP4 and JP5 and UART lines going to the MAX232 chip are selected via jumpers JP1 and JP2 : locate these jumpers on the card and install the 3 pins single-row male connectors. - Install the voltage regulator : on the component side if you choose a TO220 package or on the solder side if it is a TO252 SMD package. - Solder the two +5V pins and the two GND pins. - You can install R2, R3, R4, R5 and C5, C6, C7, C8 (low pass filters on the DAC outputs) if such filters are needed. - The Reset switch S1 and the 5.08 mm terminals blocks can be now soldered thus ending the construction.

2. Testing your board. - Before powering your card you must set the jumpers : Appendix 4 shows how to proceed. - Don't put any chip in the U1, U4 and U5 sockets : connect the power wires to a power supply set at 8 Volts. Check the power supply current (less than 5 mA) and the voltage between U1 pin 20 and ground, then between U4 pin 16 and GND and between U5 pin 1 and GND. These voltages must be around 5 V. If not, check solders on the card. - You can now install a 18F2525 PIC programmed with the simple “LED18F2525.hex” file in the U1 socket and check that the LED blinks. - Refer to the Microchip notes for information about the ICSP interface before using it, if you are not familiar with it. Beware of excessive loading of the programmer by external devices possibly connected to the PIC pins used by the ICSP.

Conclusion. The PICARD80 is a versatile development board that can be adapted to many environments. It can be used as a stand-alone card or included in a more complex design.

Appendix 1 : Part list All SMD parts are 0805 package. Components without any comments are through holes packages.

1. Resistors. R1 : 4.7 k Ω R2, R3 : 470 Ω (may be changed for other band pass) R4, R5 : 470 Ω SMD ( “ “ “

)

2. Capacitors. C1, C2, C9 : 10 uF Tantalum Note : C1 and C2 values may be modified depending on the regulator you select. C3 : 0.1 uF C4, C10, C11, C12, C13, C14, C15 : 0.1 uF SMD C5, C6, C7, C8 : 470 pF SMD (may be changed for other band pass) C16, C17 : 22 pF SMD 3. Miscellaneous D1 : foolproof diode (1N4003 or low drop Schottky) L1 : 15 uH (a simple wire strap may be used if inductor not available) Q1 : 20 MHz crystal U1 : PIC 18 pins microcontroller U2 : low drop LM1117 U3 : 7805 U4 : MAX232A or equivalent U5 : MCP4822 S1 : 4 x 6 mm, 4 pins PCB type push-button switch All jumpers are 2.54 mm pitch (0.1”) type. All terminal blocks are 5.08 mm pitch (0.2”) type

Appendix 2 : solder side parts layout

Appendix 3 : Through holes connections - Connections between top and lower planes are shown below : - 13 yellow stars show the connections between solder side tracks and top side ground plane. - 4 yellow polygons show where to solder small wires between top and bottom ends of Tracks 1 and 2 through holes

Appendix 4 : Jumpers Settings Several jumpers must be properly inserted before powering the card. - DAC jumpers JP3, JP4, JP5 : they allow connections of RC5, RC3 and RC2 PIC pins either to the MCP4822 SPI control lines or to the corresponding connectors of the Port C Terminal block. - RS232 jumpers JP1 and JP2 : they connect RC6 and RC7 PIC pins to the MAX232A lines or to the Port C Terminal block. - Jumper JP6 is used to connect RA5 line to the on board LED. Exemples : - Figure 1 below shows the jumpers (yellow rectangles) inserted for RC2, RC3, RC5, RC6 and RC7 PIC pins connected to the Port C Terminal block, the LED being connected to the RA5 line.

Figure 1

- Figure 2 shows the jumpers for DAC and RS232 selection and the LED still connected to RA5.

Figure 2