2x16 display trouble

MrOzmo

I have a problem using a ilm-216 lcd display on the homework board. I'm getting funny looking characters instead of letters. I used : serout 14, 813, ["hi"]. I'm very new at this and any suggestions would be appreciated. Also the codes 14,15 don't turn backlight on.

Martin_H

Does it look like whole rows have dropped out, or are they lit but displaying gibberish? If it is the former it is likely a defect in the LCD. Gibberish might be how it's hooked up.

MrOzmo

Its gibberish. The initial power screen reads fine. Please don't give up on me. i've been trying for years.

Martin_H

Gibberish in this case may be a good thing. I Googled your serial LCD model number and found this support page: http://www.seetron.com/ser_an1.htm. In reading the documents, it uses RS-232 or inverted TTL logic levels. So a serout on pin 14 would use normal TTL logic levels (at least I've never seen anyone send inverted using serout).

So a serout resulting in gibberish would be expected. But what to do about it? You could poke around on their site and see if they have any microcontroller wiring examples. They might suggest how to hook it up to the home work boards RS-232 output. If you can't find that an inverter chip could flip the sense of your serout output and make it what the LCD expects.

BTW here's a good read on the BS2's serout command which also mentioned inverted RS-232 logic levels:

http://www.parallax.com/dl/docs/cols/nv/vol1/col/nv16.pdf

In that PDF I found this tidbit that may help you

Polarity. In our discussion of serial theory above, you may have noticed that the voltages
were backward, with –10V meaning 1 and +10V meaning 0. RS-232 signals are inverted
with respect to the digital convention of 0V = 0 and 5V = 1. So when you want to talk
directly to an RS-232 device, you must select inverted polarity by putting a 1 in bit 14 of
the baudmode (by adding or ORing hex $4000 into it). RS-232 line drivers, chips
designed for converting digital signals to RS-232 voltages, also invert those signals. So to
talk through a line driver you’d put a 0 in bit 14.

Good luck

MrOzmo

I used this, and all is working now, thanks for the help, someday I might understand what I did.
PAUSE 1000
DO
PAUSE 1000
N2400 CON $418D
SEROUT 14,N2400, ["hijkjhkjhj"]
PAUSE 1000
LOOP

Its the n2400 con $418d that did it.