Parallax 16x2 LCD display

David Betz

I used a Parallax 16x2 LCD display in a project my son is trying to use in Africa. Of course, it is giving him trouble and I'm nowhere near there to help him figure out what is going wrong. It seems to go into its demo mode even though the baud rate switches are set to 19,200 baud. Is there anything that could cause that to happen?

Electrodude

Was it dropped or something? I have a 4x20 one that I dropped a few years ago, and Switch 1 broke, so I can only use demo mode and 9600 baud now. If I flip Switch 1, I don't feel or hear a click, only a small lump, and the LCD always thinks that switch is off, but Switch 2 works fine and clicks properly.

When I broke mine, I couldn't find any good way to fix it short of hacking the switches off and solder globbing the terminals together, which I did not do. I only just found a permanent use for it a month or so ago, as a monitor display for my Raspberry Pi server, and 9600 baud is plenty for that (I can't see why you'd need anything higher for such a small display - it's enough to PWM the backlight intensity via serial commands).

David Betz

Apparently it works fine in demo mode but behaves erratically when switch to 19,200. I don't think it was dropped but it was carried on a plane without adequate padding so it may have banged up against other stuff like an ActivityBoard. Hard to say.

Chris Savage

David,

One thing to note, the mode switches are only read are startup. If they're changed after it is powered up they won't affect anything. So if the issues with the 19,200 baud are during operation I doubt that it is the issue.

David Betz

Chris Savage wrote: »

David,

One thing to note, the mode switches are only read are startup. If they're changed after it is powered up they won't affect anything. So if the issues with the 19,200 baud are during operation I doubt that it is the issue.

I sent him firmware images for 2400 and 9600 baud as well as the original 19,200 in case maybe the switches got stuck in some position other than what we had originally planned. Not sure what else I can do at this distance.

T Chap

I use many of these, only a few over the years that were defective out of box. You cannot hot swap plugs for this GND/5V/sig or it can easily kill it. On power up, you need the switches where you want them, they cannot change after power up. Did it ever work at 19200? What happens if you power up in 00, 01, 10, 11 on the display.

David Betz

T Chap wrote: »

I use many of these, only a few over the years that were defective out of box. You cannot hot swap plugs for this GND/5V/sig or it can easily kill it. On power up, you need the switches where you want them, they cannot change after power up. Did it ever work at 19200? What happens if you power up in 00, 01, 10, 11 on the display.

This one wasn't defective out of the box. It worked fine until it was shipped to Africa. I'll have to let you know later about how it works in the other modes. My son said he'd test them later.

T Chap

If a signal is sent to the lcd when the lcd has no power, it can fry it. I have fried a few like that. The demo can still work though as the input only is fried.