This file contains a list of know problems and issues that some constructors
have experienced with building the Digital IC Tester featured in the
October 2002 issue of EPE.

Please read the entire contents of this file before trying any of the 
procedures outlined as you might be able to save yourself a lot of time
in the long run.

Firstly, an oversight meant that the configuration bits required when programming
the PIC were never documented. The updated .ASM file contains these as part of
the comments but I’ve listed them here for completeness.

Bit 13    CP1 - 1 Off
    12    CP0 - 1 Off
    11    DBG - 1 Off
    10        - 1 Off
     9    WRT - 1 Off
     8    CPD - 1 Off
     7    LVP - 0 Off
     6    BOR - 0 Off
     5    CP1 - 1 Off
     4    CP0 - 1 Off
     3    POR - 0 On  (IMPORTANT)
     2    WDT - 0 Off (IMPORTANT)
     1    OS1 - 1     (IMPORTANT)
     0    OS0 - 0     (IMPORTANT)

Bits 1 and 0 should be set for High Speed XTAL...

These settings are taken from the TK3 configuration screen.


First checks.....

Make sure you have followed the article instructions carfully.
Also, re-read the 'First Tests' section of the article again.

Make sure you are using a 20MHz version of the 16F877 PIC and have a 20MHz 
crystal fitted. (The software won’t run at any other frequency without modifications)

Make sure you have the cable type wire links located to the left of the 9 way
female cannon socket set for the type of cable you are using. Also, note that 
socket is a female type and not male. You cannot fit a male connecter to the PCB.
This means that you cannot use a true null-modem cable which is correct as 
the IC Tester is a DTE (Data Terminal Equipment).


Next............

Does the red LED (D4) and the green power LED (D1) light when the board is 
first powered up (there was a mistake in the original article and the red LED
was shown the wrong way around but circuit diagram was correct).

I'm going to assume your using COM1 and a straight through serial cable.

Go into hyper-terminal and set it for 19200 Baud & COM1.
You should be able to open the connection and not receive any errors.
(This means that no other software/drivers on the PC is using/locking the 
serial port)

Remove the power to the board until told to re-connect.
Remove the MAX232 and the PIC. Connect your straight-through serial cable to 
the board and computer.

The two solder links to the left of the serial connector on the IC Tester 
board should be connected correctly (i.e. NOT crossed for a straight cable).

Type something in to Hyper-terminal and nothing should be seen.

Now, short together the RS232 input and output pin on the MAX232. Pins 14 
and 13. (Remember that the power should still be off).

Short together these pins on the IC socket (without the MAX232 fitted) with 
a small piece of wire. This will effectively create a loop - shorting the TX and RX pins.
Type something into Hyper-terminal and this should be seen now.

This proves the PC, cable, socket and soldering is ok to this point.

Next, there are two wire links at the bottom of the board to the right of 
the PIC socket and to the left of RM3. Short these two together (remember that
the PIC is still removed at this point)

Remove the jumper wire from the MAX232 socket and re-fit the MAX232.
Connect power to the board and switch on. The green LED (D1) should light.
Type something into Hyper-terminal and it should be echoed back.
This proves that the MAX232 is running correctly.
If not, check around the MAX232 for shorts/solder bridges.
Check that 5v is present at pins 16 and 15.
Check that the capacitors are fitted the correct way around.
Try another MAX232 chip.

Power off the board.

If this all works, remove the short of the two links, refit the PIC and 
power up the board.
When power is applied, you should see 'Ready' appear in HyperTerminal.
Press the '0' (zero) key on the PC keyboard and you should see the IC Tester 
respond.

If the board still doesn’t work then there could be a problem with the PIC.
Try to re-program the PIC again.

Also, check the following:

The 9 pin socket on the board MUST be a female and NOT a male connector.

Never attempt to run the board with the MAX232 bypassed.

You might have problems programming the PIC on board with the resistor pack 
RM2 fitted.

There was an error in the article and the red LED D4 was the wrong way 
around (circuit diagram is correct). If you need to rotate this LED, be very 
careful that the PCB tracks don’t break.

Check for solder bridged tracks around RM2 and the underside of the ZIF 
socket causing short circuits.

Check that +5v is present at TP1 during test testing cycle in case TR1 is 
damaged.