Need help wiring up this LCD character display. - Page 1
Forum section: electronics / beginners

author: MassDestruction
author_rank: Contributor
timestamp: December 04, 2017, 04:13:45 pm
content: Hey EveryoneI'm currently trying to wire up a ERC1602FS-2 display to my microcontroller and get it to work. Currently it doesn't do that. Also the code I have on there should work fine for this LCD so I'm sure it's a hardware issue.The micro operates at 5V and the lcd operates at 3.5V. To regulate the voltage I'm currently using voltage dividers to bring the voltage down to 3.5V. I know that voltage dividers are discouraged, but I couldn't get my hands on a linear voltage regulators at the time.So my current questions are.1. Do the bus datalines to the LCD need to operate at 3.5V also?(They are currently at 5V)2. Could the voltage dividers cause the LCD to not operate properly?I provided the datasheet and interface document below.Datasheethttp://www.buydisplay.com/download/manual/ERC1602-2_Series_Datasheet.pdf] http://www.buydisplay.com/download/manual/ERC1602-2_Series_Datasheet.pdfInterface Documenthttp://www.buydisplay.com/download/interfacing/ERC1602-2_Interfacing.pdf

author: Ian.M
author_rank: Super Contributor
timestamp: December 04, 2017, 04:29:14 pm
content: 1. Yes. See itsNT7603controller datasheet. None of the I/O lines controlling it may exceed its Vdd2. Yes, but we'd need to see your exact schematic to know one way or another.Worst case you may already have killed your LCD!

author: MassDestruction
author_rank: Contributor
timestamp: December 04, 2017, 04:53:09 pm
content: Quote from: Ian.M on December 04, 2017, 04:29:14 pmThank you Ian. I'll post my schematic as soon as I get home.How would I properly regulate the voltage going through the bus lines? Should I get a 3.5V linear voltage regulator for each databus line?

author: Ian.M
author_rank: Super Contributor
timestamp: December 04, 2017, 07:21:19 pm
content: No. Regulators are unsuitable for data lines. Normally. linear regulators are only used to derive lower voltage power rails. When we see your schematic, (with component values) we can assess the odds on whether or not you may have killed it.Correctly designed potential dividers are usable for downwards level translation, but not for bidirectional use unless you drive them from a bidirectional 74HCT buffer. There are purpose designed level translating chips available and often its a good idea to use one rather than hacking something together from discretes.

author: MassDestruction
author_rank: Contributor
timestamp: December 08, 2017, 10:42:27 pm
content: Quote from: Ian.M on December 04, 2017, 07:21:19 pmSorry for taking so long. Here is the schematic.

author: Ian.M
author_rank: Super Contributor
timestamp: December 09, 2017, 01:18:23 am
content: That doesn't look good at all. All 3.3V supply rails need to be fed from either a LDO regulator or a switching 'buck' regulator, not from a potential divider. Also you need level converters in all the control and data lines, and the data ones must be bidirectional if yo want the capability to poll the display's busy flag and read back data from it. Its likely the display is already damaged by over-voltage on its control and data lines, but its possible that its survived by loading down the data lines, because you FUBARed its Vdd supply.Note that V5 is NOT a 3.3V supply pin for the display - its the bottom end of the LCD waveform voltages divider chain and is the point at which you would apply the contrast control voltage. Try connecting a 10K pot, one end to Gnd, the other to a 10K resistor going to +3.3V, wiper to V5 pin.For the control and data lines, the easiest option would be to use aTXB0108octal bidirectional level translator. Make sure you get it the right way round as its A port side is not 5V tolerant.