PICcom is a general purpose serial port development tool designed to aid debugging of standalone micro controllers such as Microchip's PIC series. Data sent from the micro can be displayed in one of eight display windows or the 'Terminal' window. The display 'Format' can be set to Binary, Hex, Decimal or ASCII. Communications from the micro controller to the PC is by the serial port and one way only (transmit) which can be implemented using a single I/O pin. A simple code library is provided for addition into your target firmware to implement the serial port protocol. This means that PICcom can be used with any device in the PIC family range.

Software

The software for implementing PICcom consists of the files listed below which is provided in a single install file. Run the installer and then create a Windows start icon for the PICcom.exe executable, setup files and example library code are installed to C:\Program Files\PICcom.
 

File	Ver	Date	Description
PICcomSetup Size: 200K	1.0	15/5/2003	PICcom self extracting installer
	1.1	15/5/2003	Windows software Win98/2000/XP
	1.0	15/5/2003	4MHz example code library
	1.0	15/3/2003	10MHz example code library
	1.0	15/5/2003	20MHz example code library
	1.0	27/4/2003	Demonstration code (4MHz)

Serial Interface Lead

Connect the serial lead DB9F female connector to the micro controller board with the following cable. Ideally the 2 pin connector should be a polarised 0.1" PCB connector. Unpolarised connectors such as those used on PC reset switches can also be used as they are unlikely to cause damage to the PC or micro controller if plugged in upside-down.

Warning: Failure to connect to the correct DB9F serial pins may result in permanent damage to the micro controller or PC. Always measure the voltage across the two pin connector before connecting up. This should read less than 0.1V (floating input to PC).

Hardware Testing

To test the serial port start the PICcom program, set Terminal to 'CH1', set the Format of CH1 to 'ASC' and press 'Run'. With the lead disconnected from the micro controller short out pins 2 and 3 on the DB9F connector (loopback test). This should result in a stream of 'S' characters being displayed in the terminal window and in CH1.

Now you need to test the interface. I would recommend starting with a board that contains a PIC16F84 and a 4MHz crystal. Plug the 2 pin connector into the micro controller board.  If you connect the Ground to PIC-pin 5 and TX to PIC-pin 6 (PORTB,0) this will work with the default software settings. Program the 'Demonstration code' hex image into the PIC, press 'Run' on PICcom and power up the board. This should result in the screen image shown at the top of this page.

   Using PICcom

  

To add PICcom to your design it is necessary to select the code library that matches the crystal or ceramic resonator frequency being used (4/10/20MHz). This is because the serial bit rate is coded into the library file as a function of the processor clock cycle. Note that external or internal R/C oscillators may not be stable or accurate enough (better than 5%) to achieve reliable serial communications. The code library is not interrupt driven and is simply called with the data value in 'Wreg'. The call address 'SETCH0', 'SETCH1' etc. determines which one of the eight display windows will be updated. The following steps describe how to integrate the code library.

1. Add the three/four file registers: PICCOMT, PICCOMD and PICCOML (PICCOMH).
2. Add the PICcom Port and Pin definitions: PCPORT, PCPIN.
3. Add the main PICcom code segment.
4. In the setup code after reset set the PICcom port pin direction and call PCINIT to initiate the interface.
5. Add calls to PICcom whenever you need to debug your code eg,

    MOVLW   'M'        ;Display 'M' it window 2
    CALL    SETCH2

    MOVFW   TEMP0      ;Display file register TEMP0 it window 7
    CALL    SETCH7

Since the call to SETCHx will result in a short software delay as the data is transferred to the PC it is important to add the calls carefully.  Typically the transfer takes 220uS at 115200BPS so the best place to make SETCHx calls is after a time crucial action has completed or before a delay.

The PICcom 'Terminal window' allows multiple transfers to be captured and displayed.  One or more of the 'Display windows' can also be directed to the 'Terminal window' in any 'Format'. When the terminal window receives data in ASCII format (ASC)  characters in the range '  ' to '~' (0x20 to 0x7E) will be displayed. ASCII '0x0A' will result in line feed, ASCII '0x7F' will result in the window being cleared.

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