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Character LCDs / Re: NHD-0420H1Z-FL-GBW-33V3 pull-ups and pull-downs in 4 bit mode
« on: December 10, 2014, 12:09:49 PM »
Great, thank you. I did see the diagram in the data sheet, in addition to the internal wiring diagram in the ST7066U manual showing pull-ups on RS and R/W but not E - both great references. It seemed clear but I wanted to get a confirmation just in case.
We are stuck on the use of the NHD-0420H1Z-FL-GBW-33V3. The display does illuminate when powered and initialized but no cursor or characters are ever visible. It also seems as if the DDRAM addresses are not incrementing when data is written to them or event when an explicit address command is sent to the controller. Oddly, the BF does seem to be working...
I was hoping there was a requirement for external components and that perhaps floating lines were responsible - on the off chance they would stop the controller from initializing properly if they were absent.
Given that is not the case - can you suggest a means to troubleshoot the internal state of the controller? How can we verify it is in fact initialized? Is there, for example, a DDRAM location I can attempt to read that holds the current Function Set data? I could write various values via Function Set and read them back to verify their application.
Another thought is that perhaps the voltages to VDD, V0, and LED+ are misconfigured - high V0 for example (V0 = VDD). But if that were the case I would expect the call to set the AC or calls to write characters would result in those address values coming back with the BF.
We are stuck on the use of the NHD-0420H1Z-FL-GBW-33V3. The display does illuminate when powered and initialized but no cursor or characters are ever visible. It also seems as if the DDRAM addresses are not incrementing when data is written to them or event when an explicit address command is sent to the controller. Oddly, the BF does seem to be working...
I was hoping there was a requirement for external components and that perhaps floating lines were responsible - on the off chance they would stop the controller from initializing properly if they were absent.
Given that is not the case - can you suggest a means to troubleshoot the internal state of the controller? How can we verify it is in fact initialized? Is there, for example, a DDRAM location I can attempt to read that holds the current Function Set data? I could write various values via Function Set and read them back to verify their application.
Another thought is that perhaps the voltages to VDD, V0, and LED+ are misconfigured - high V0 for example (V0 = VDD). But if that were the case I would expect the call to set the AC or calls to write characters would result in those address values coming back with the BF.