16x2 displays gibberish only on 1st run after power up
Moderators: adafruit_support_bill, adafruit

Forum rules
Talk about Adafruit Raspberry Pi® accessories! Please do not ask for Linux support, this is for Adafruit products only! For Raspberry Pi help please visit: http://www.raspberrypi.org/phpBB3/

16x2 displays gibberish only on 1st run after power up

by Zygo on Wed Mar 13, 2013 3:49 pm

I am using the 16x2 LCD Pi plate and have found that when I run any of the test programs as the first thing after powering on the Pi, I get gibberish. However, if I then close the program and rerun it, it works fine. Every subsequent running of any program running the LCD works fine, until the next power off.

The gibberish looks like what was happening before I changed busnum to 1 (it is currently set at 1)
Zygo
 
Posts: 4
Joined: Wed Mar 13, 2013 3:15 pm

Re: 16x2 displays gibberish only on 1st run after power up

by adafruit_support_bill on Wed Mar 13, 2013 4:08 pm

Could be a marginal solder joint on one of the data lines. Post photos of the front & back of the plate.
User avatar
adafruit_support_bill
 
Posts: 31900
Joined: Sat Feb 07, 2009 10:11 am

Re: 16x2 displays gibberish only on 1st run after power up

by Zygo on Wed Mar 13, 2013 4:14 pm

Ok, I will when I can, but it is very repeatable. Feels like a software related issue. Always a problem on first run, never after.
Zygo
 
Posts: 4
Joined: Wed Mar 13, 2013 3:15 pm

Re: 16x2 displays gibberish only on 1st run after power up

by adafruit_support_bill on Wed Mar 13, 2013 4:50 pm

Feels like a software related issue. Always a problem on first run, never after.

Are you using the code from the tutorial? We have a few thousand of these out there and this is the first report of this kind of problem.

I do know that these displays are sensitive to noise and/or bad connections. One glitch during a command sequence and you have to reset the display to recover.
User avatar
adafruit_support_bill
 
Posts: 31900
Joined: Sat Feb 07, 2009 10:11 am

Re: 16x2 displays gibberish only on 1st run after power up

by Zygo on Fri Mar 15, 2013 3:50 pm

I found out the problem!

I needed go through all the modules and set busnum=1. I had done so in my code and in Adafruit_CharLCDPlate, but not in the imported modules(Adafruit_MCP230xx and Adafruit_I2C). Also, although I2C is supposed to autodetect the bus number, it didn't work until I replaced the autodetect stuff with "1".
Zygo
 
Posts: 4
Joined: Wed Mar 13, 2013 3:15 pm

Re: 16x2 displays gibberish only on 1st run after power up

by adafruit_support_bill on Sat Mar 16, 2013 6:46 am

Great! Thanks for the follow up.
User avatar
adafruit_support_bill
 
Posts: 31900
Joined: Sat Feb 07, 2009 10:11 am