INIT GLCD 128x64 SED

smatjaz · Joined: 28 Jun 2004 Posts: 62

Hello.

I have a circuit (ATXMEGA128A3U) with a graphical display 128x64 - glcdks108.lib. The device includes a relay - the pump. When switching relay, it sometimes happens that the display freezes. The circuit operates normally.

I need to re-initialize the display during operation of the program.

I tried using the command:

albertsm · Joined: 09 Apr 2004 Posts: 5921 Location: Holland

you can use : !call _set_display
This will init both of the ks108 chips.

JC · Joined: 15 Dec 2007 Posts: 586 Location: Cleveland, OH

Also, it is desirable to find the cause for the erratic LCD operation and fix the underlying cause, when possible.

In this case does the relay have a reverse biased diode across the coil, (or another snubber circuit)?
It sounds like the relay is likely generating a voltage spike when it is turned off, and that is interfering with the LCD, and perhaps with the uC itself.

Do you have AVcc tied to V+, (optionally through an LC filter)?

Do you have a by-pass cap, e.g. 0.1 uF, across each Vcc/Ground and AVcc/Ground pin pair, mounted very close to the micro itself?

If the LCD is at a fair distance from the micro, or if the Relay is at a fair distance from the micro, then additionally their wiring can act as antenna and pick up EMI from the relay coil, from the contact arc, and perhaps from the load the relay is switching on and off.

JC

smatjaz · Joined: 28 Jun 2004 Posts: 62

Hello.

The circuit has, together with the display, approximately 8cm long wires.
This is probably the cause of the problem.

On the connector pins I added a 10K resistor strip. System works better, but still periodically display freezes.

I will try with command:

smatjaz · Joined: 28 Jun 2004 Posts: 62

Thank You.

It works just as I wanted.