Wiring a 633 or 634 to a Basic Stamp2p40


New member

I am kind of new to using LCD and recently picked up a 633 and 634 for some projects.

I would like to use these with some basic stamps (2C or 2p40) but have some questions.

1. On the sample basic code for driving the serial port of the lcd it suggests jumpering jpe. I see that this is a two position dip switch. Should both dips be in the on position or off. I assume on

2. I see that the lcd header requires a ground (no problem there), two +5vdc sources one for led and one for lcd. Not sure which to use or both.

3. What are SPI_CS, SPi_Clk, SPI_Busy and how are they wired and used.

4. I assume that the serial output of the stamp is connected to the lcd via a db-9 straight thru cable.

Answers to these questions would be most appreciated.


Dennis Friedman
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CF Tech

Thank you for your post.

Please check the "Connecting your LCD" section of the CFA-634's data sheet. That should answer most of your questions.

The DIP switches are for changing the baud rate.

The SPI interface can be selected instead of the RS-232. Please see the "SPI Timing Diagram" in the data sheet for details.

The LCD can talk "real" RS-232 levels or "inverted" RS-232 at 0-5v levels. If the stamp does not have a RS-232 level converter on it, then logic level may be an easier way to connect the LCD.

The "logic" and "backlight" supplies are separated to allow some flexibility in designs that need low power. If power is not a concern for you, you can simply connect them together.


New member
Thanks for the reply


I appreciate the quick turnaround on my questions. I have downloaded the pdfs. I tried looking for them on my own but did not see them listed anywhere. I must have missed them.

I am using a basic stamp homework board for my project and do not know if there is an rs232 level converter or if the rs232 signal is inverted. Do you know this board or could you suggest the appropriate methodology for determining such.

I downloaded the crsystalfonz lce basic sample and then attached my mulitimeter to pin 3 to try to determine output voltage. Maybe I should just try a logic level test instead.

Any additional help would be most appreciated.

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CF Tech

Please post a link to the data sheet for your stamp board, and I'll see if I can figure out how it should be connected.