Post by thread:PIC16C65A and LCD problem!!

Friends, I am using an LCD (2X20) to display some results of a test performed by a PIC16C 65A. The PIC performs all of it's tests and display's the appropriate data for t he appropriate tests. Unfortunately, the first two spaces on the top line seems to have an incorrect character (It's supposed to be blank). The funny thing is t hat when I unplug the LCD from it's socket (leave the PIC circuit powered up) an d then plug it right back in, the "trash" characters aren't there anymore. But i f I turn off the whole circuit and then restart it, the "trash" characters are s till there. It's a mystery to me!? I would appreciate any/all help I can get!! T hank you all! Best regards, Steven Steven Kosmerchock Email: spam_OUTsteve.kosmerchockTakeThisOuTcelwave.com http://www.geocities.com/researchtriangle/lab/6584

part 0 1088 bytes Just a thought. -----Original Message----- From: Steven Kosmerchock [SMTP:.....Steve.KosmerchockKILLspam@spam@CELWAVE.COM] Sent: Saturday, 07, November, 1998 08:54 AM To: PICLISTKILLspamMITVMA.MIT.EDU Subject: PIC16C65A and LCD problem!! Friends, I am using an LCD (2X20) to display some results of a test performed by a PIC16C65A. The PIC performs all of it's tests and display's the appropriate data for the appropriate tests. Unfortunately, the first two spaces on the top line seems to have an incorrect character (It's supposed to be blank). The funny thing is that when I unplug the LCD from it's socket (leave the PIC circuit powered up) and then plug it right back in, the "trash" characters aren't there anymore. But if I turn off the whole circuit and then restart it, the "trash" characters are still there. It's a mystery to me!? I would appreciate any/all help I can get!! Thank you all! Best regards, Steven Steven Kosmerchock Email: .....steve.kosmerchockKILLspam.....celwave.com http://www.geocities.com/researchtriangle/lab/6584

On Fri, 6 Nov 1998, Steven Kosmerchock wrote: > Friends, I am using an LCD (2X20) to display some results of a test > performed by a PIC16C65A. The PIC performs all of it's tests and > display's the appropriate data for the appropriate tests. Unfortunately, > the first two spaces on the top line seems to have an incorrect > character (It's supposed to be blank). The funny thing is that when I > unplug the LCD from it's socket (leave the PIC circuit powered up) and > then plug it right back in, the "trash" characters aren't there anymore. The LCD needs to be initialized according to the data sheet sequence, or reset by a fast power on flank. When you remove it from the socket and put it back you do just that. The power on flank for the whole circuit is much slower. If you don't want to use the whole funky initialization sequence, use a transistor switch to turn on the LCD power abruptly from a PIC pin or from the reset chip that drives the PIC (if any). > But if I turn off the whole circuit and then restart it, the "trash" > characters are still there. It's a mystery to me!? I would appreciate > any/all help I can get!! Thank you all! The HD47xxx chips are genuine CMOS parts and as such they will keep the bit patterns for several seconds or minutes without power applied (using the very low voltage remaining in the decoupling caps). It is known that some CMOS timekeeping chips need to be shorted without power applied for up to 5 minutes to convince them to forget some of what they contain. If you use the initialization sequence with the LCD it will be erased properly by the time it lights up. imho the missong reset pin from the industry standard LCDs is a pain in the rear. Peter

You could throw a rock in any direction and hit someone that knows more on this topic than I do. But in my limited experience, if 'junk' appears on the pins of an LCD display, just about anything can happen, most of it defying logic. Try checking Power up sequencing Double check what you're actually sending the display Check for adequate timing between rise and fall on enable line. On Fri, 6 Nov 1998, Steven Kosmerchock wrote: > Friends, > I am using an LCD (2X20) to display some results of a test performed by a PIC16C65A. The PIC performs all of it's tests and display's the appropriate data for the appropriate tests. Unfortunately, the first two spaces on the top line seems to have an incorrect character (It's supposed to be blank). The funny thing is that when I unplug the LCD from it's socket (leave the PIC circuit powered up) and then plug it right back in, the "trash" characters aren't there anymore. But if I turn off the whole circuit and then restart it, the "trash" characters are still there. It's a mystery to me!? I would appreciate any/all help I can get!! Thank you all! > > Best regards, > Steven > > > Steven Kosmerchock > Email: EraseMEsteve.kosmerchockspam_OUTTakeThisOuTcelwave.com > http://www.geocities.com/researchtriangle/lab/6584 >

> Friends, > I am using an LCD (2X20) to display some results of a test performed by a PIC1 6C65A. The PIC performs all of it's tests and display's the appropriate data for the appropriate tests. Unfortunately, the first two spaces on the top line seem s to have an incorrect character (It's supposed to be blank). The funny thing is that when I unplug the LCD from it's socket (leave th e PIC circuit powered up) and then plug it right back in, the "trash" characters aren't there anymore. But if I turn off the whole circuit and then restart it, the "trash" characters are still there. It's a mystery to me!? I would appreciate any/all help I can get!! Thank you all! > Sounds like they might be part of some sort of auto baud-detect. The first few baud rates failed (and the check character shows as garbage) and the last one was right. Once the baud rate is established, you could disconnect and re-connect the LCD without re-handshaking. You didn't say much about the LCD so I'm just thinking aloud here... Mark Hillier President, HVW Technologies Markspam_OUTHVWTech.com Tel:(403)730-8603 Fax:(403)730-8903 Visit our web site: http://www.hvwtech.com

I had the same problem initially, even after meeting the power-up spec, on a HD47xxx display. Using the fancy software intialization sequence cleared everything right up. Besides, every decent software design should always reset all peripherals after power-up (learned that the hard way). -Ed VanderPloeg Agile Controls @spam@evanKILLspamdirect.ca > {Original Message removed}

yes, it's probably the init routine. here is a quick note from my data specs, power on wait more than 15ms after vdd rises to 4.5vdc write 0x30 function set wait more than 4.1ms write 0x30 function set wait for more than 100us (then resume normal data transfer) michael You may leave the list at any time by writing "SIGNOFF PICLIST" in the body of a message to KILLspamLISTSERVKILLspamMITVMA.MIT.EDU. {Original Message removed}