would be possible. However, if you wish to use USB, a better choice would be to use the GP3X board which
requires less custom wiring.
You should check your work before installing IC1 in its socket. Power the board up using your choice of
methods and verify that 5V appears on the +5V connector.
Next, proceed to the Final Checkout section below.
Final Checkout
If you are using a MAX232, you can also perform an echo test to verify the port circuitry before you install IC1.
Connect your PC to the DB9 connector using a straight RS232 cable (assuming you did not modify the
DTEDCE jumper on the GP3X; otherwise, use a cross cable). Open a terminal program to the correct port and
make sure local echo is off as well as hardware handshaking. The baud rate is not important (use 57600 baud if
you like since that is the speed you will use later as well). Typing on the terminal should have no effect at this
time. If you see what you are typing you don't have local echo turned off in your terminal program. Short pins
17 and 18 on the IC1 socket and apply power to the board. Now when you type, you should see the characters
your type appear. Removing the short should stop your terminal program from showing you what you type. This
test will show that the RS232 communications is working correctly. You can perform the same test with the
USB daughter board or cable using a USB cable and the appropriate COM port.
Once these checks are complete (or you are feeling lucky) you can fit a jumper on the Pgm Run header so that
the center pin connects to the pin closest to the word Run on the GP3X. For the GPMPU40 the jumper at JP7
should have a short between JP7-2 and JP-3. For the GPMPU28 connect JP1-3 to the 5 volt supply (pin JP1-11,
for example). Install IC1 and power up the board. The GP3 chip has a program built in that will blink the
onboard LED 10 times, pause and repeat. If you did not install either D1A or D1B as built-in LEDs, you can
temporarily connect an LED to the LED pin of J1. You can also monitor the output with a voltmeter as the
output is slow (about 2Hz).
If the communications test passed and the LED blinks, congratulations, your GP3 is working and you can
proceed to the Software section of this manual.
Software
The GP3 connects to a PC or other host device via the RS-232 port. The GP3 is a DCE device, so you can use a
straight cable to connect directly to a PC. The PC sends commands to the board using 57600 baud serial data.
To make things simpler, you can download libraries that interface your programming language to the GP3
seamlessly. Most Windows-based languages can use ActiveX controls or DLLs, and both are supplied.
To use the GP3 for a particular function, you can either write custom software in a variety of languages, use an
application provided (such as GP3DAQ) or use GP3EZ to build a “script” without programming. In addition,
GP3 scripts can be downloaded to the GP3 where it can execute without connection to a PC.
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