Propeller, Scott Edwards Serial Backpack

arakarnouzian

·I am trying to interface my propeller with a scott edwards serial backpack LCD module.
·is there anyone who has a driver and a sample program for this task?

Mike Green

It's a serial LCD module, so any serial driver (Simple_Serial, FullDuplexSerial, etc.) should work. Read the Scott Edwards Backpack Module documentation for details of special control codes.

JonnyMac

The Scott Edwards LCDs use inverted serial so you'll want to use a negative baud rate. For example, if you declare an LCD object of type "simple_serial", you could initialize it to use a SEETRON display at 9600 baud on pin 0 like this:

lcd.init(-1, 0, -9600)

The -1 means no RX pin, 0 is the pin to use for TX, and -9600 means 9600 baud, inverted.

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Jon McPhalen
Hollywood, CA

David B

I've got a couple of these. Here's some code I've used to run it. It's not great code but it works.

The Seetron LCDs need 5 volts for power.·Mine will sometimes accept 3.3 volts at the input for the signal, but there are a couple of problems with doing that. One is that if the 5 volts rises just slightly, like to 5.1 or 5.2 volts, it can pass the switching threshold and the display may no longer work. Another problem is the displays (at leat the versions I have) must be powered up with the data line low or else it goes into diasgnostic mode.

At the top of my code is a schematic of a one transistor interface that works pretty well to both drive the data line with 5v, and make sure it initializes properly.

JonnyMac

David makes good points. One of the features of SEETRON backpacks is that they'll take RS-232; this is why the baud mode is inverted. What this also means is that the serial line goes through a divider so you're not getting 3.3v to the serial input pin; I've had a couple act flaky because of this.

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Jon McPhalen
Hollywood, CA