development board Version 3

[jagjit (Jag) sehra]

Hi Folks,
I am new to this forom so hello to everyone, I have got version 3 development board and am using flowcode version 3. I was looking at the circuit diagram for the board which is available on the matrix multimedia website. Am I right in thinking that the board uses Port A and port B for I/O. I guess this is due to the fact that the board can use a variety of PICs and the board must be designed assuming the smallest devise. However the thing that I cant understand is that it seems that only four bits of Port A are bieng used RA0-RA3, if so how are these bieng expanded to eight bits for the LEDs, switches and external I/O. In flow code if I was to output the decimal number 255 to the LEDs then I would excpect all eight LEDs to illuminate, however as there really only four bits where is the hardware thats expanding it. I know this may be fairly obvious to some, however I cant find the device on the circuit diagram. Thanks in advance for your help.

Jag.

[Benj]

Hello Jag

A lot of the PICmicro devices have a reduced set of I/O connected to PortA. All 8 leds / switches on portA will only be available to the PICmicro devices without the reduced set of I/O pins.

[jagjit (Jag) sehra]

Thanks Benj for that reply, Seems I was mistaken in my thinking, I got confused looking at the circuit diagram of page 4 of the development board version 3 data sheet. Which states that Port A (RA0-RA3). Thanks for learing that up for me, however I have another small question what is a vernier sensor there a digital and analogue one on the board, does that simply mean that a sensor can be connected to the board and there a pins on the board to accept it.

Thanks in advance for your help!

[Steve]

Jag,

I think you are partially correct - the dev board only connects LEDs and switches A0-A5 to the PICmicro. The other 3 LEDs/switches are essentially redundant (although they are available via the expansion bus). The reason for this is because many chips multiplex these pins with the external clocking circuitry, which is dedicated to the RC/crystal on the dev board.

RA4 is a special case. This pin is an open-collector output on many PICmicros and needs an external pull-up resistor to drice an LED output. You can "add" this pull-up by holding down the RA4 switch while your program is running.