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Forum Index : Microcontroller and PC projects : (MM) LCD 16X2 difficulties
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bigmik Guru  Joined: 20/06/2011 Location: AustraliaPosts: 2914 |
The ones I tried work fine at 3.3V No need for pullup resistors if using DIgital out. Regards, Mick Mick's uMite Stuff can be found >>> HERE (Kindly hosted by Dontronics) <<< |
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| Talbit Senior Member  Joined: 07/06/2011 Location: AustraliaPosts: 210 |
Thanks Mick, I might disconnect the resistors in my set up over the weekend and give it a try. But as Pete has found - he is having trouble - but as he says - he's using fairly long interconnections. Talbit Talbit |
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trippyben Regular Member  Joined: 26/06/2011 Location: AustraliaPosts: 91 |
Oops my bad, miscalc. Actually with 100 ohms the sink current will be 50mA when the outputs are low as you are pulling up to 5V not 3.3V with the resistors. Therefore the smallest theroetical value would be 500ohms for 10mA sink when the outputs are low. It's obviously been proven here in this application that 10k does not work. You really do want the lowest possible value resistors when driving long cables. Why? The resistance = the source impedance when the pin is 'high', and as cable length increases, so does it's inherent capacitance and you want a low source impedance to prevent the data from being rounded off in such cases. The input high threshold on a HD44780 is 2.2V for a supply in the range 4.5V to 5.5V. (Based on the actual Hitachi HD44780 datasheet, the clones I exepct would be similar but may vary a little). So it should work just using the normal digital 3.3V outputs - no open collectors or pull-ups required! You would need to check the datasheet on the actual clone used in your displays to see if they behave the same or not. Interestingly, the HD44780 is capable of operation down to 2.7V, but you may have LCD panel drive level issues on a module designed for 5V operation running it at 3.3V. Might be worth a try, if the contrast is not badly affected at 3.3V this could help reliabiltiy over long cables. Again, the clones may be different. |
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pcaffalldavis Senior Member Joined: 17/10/2011 Location: United StatesPosts: 187 |
It is 5:00 AM here. I just got most of the components layed out on the Boiler Electgrical/Electronic Control Panel. My resistors finally came. Tomorrow, or later today after a nice long nap I will try and remove the 10k resistors I have on the Boiler Component Board for the LCD and try running it as only Digital Setpins 8 with no resistors. I have been getting what some have referred to as corrupted data. Sometimes I can see it was trying to send the correct data, but some of the characters get changed, like . Periods sometimes appear as / slashes instead. Other time both rows appear to line up a few spaces to the right of where they should (on the left margin). If running pure digital without any 10 K resistors does not make the LCD better then perhaps I'll try 5 K resistors instead. We'll get this going. I'll tell you one thing though. I'll never use a 2" x 3" veroboard again to try and fit so many components on. I ordered a bunch of 3" x 6" which would have been MUCH easier. I barely have room to get a pair of tweasers in between some of the parts! It is always good to have a spare pre built custom board in case a system fails. Like when you are away and someone else needs to do a repair, but I'll probably end up using this tiny one for the spare and build the next one for daily operations on this boiler. I can't wait to get all this together with the LCD working so I can start writing the program that will run the boiler... but that is likely going to be next month. Ain't winter great! Should be interesting. I'll update with a post regarding the LCD later today after my nap. That will likely be tomorrow for you guys down under! Pete in Hyder We're all here 'cause we're not all there. |
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| pcaffalldavis Senior Member Joined: 17/10/2011 Location: United StatesPosts: 187 |
Good news update: I pulled the six 10 K resistors from the Boiler Board and the 16 x 2 LCD has been running Digital with MM pinds set using Setpins 8 for five minutes now. Not a single degradation of the display data and I have it updating every three seconds. Just for everyone's information. I have a 10" (250 mm) 26 conductor ribbon cable from the MM to the Boiler Componet Board (BCB), and from there I have a 36" (1 Meter ribbon cable using 10 pin connectors at both ends from the BCB to the LCD. Seems to be working great! And I have the back light on a switch with a 22 Ohm resistor. All things working at this time. I guess I won't have to try it as Open Collector using 5K resistors instead of the 10 K that didn't work reliably. I'm also wondering now if I put a second LCD on the same pins using a 50' 8 conductor bell wire what will happen. I would like to have a display in the house that shows what is going on at the boiler. The primary 16 x 2 LCD will be on the outside of the boiler, but it would be nice to have another display in the house next to the house temperature sensor. Any ideas what this might do? Will I have to go back to O/C and need to try it with lower resistance resistors, like 5 K? I'm wondering about the back light. It might be nice to be able to adjust the back light brightness. What will happen if swap out the 22 Ohm resistor for a 10 Ohm to 1 K POT? Is there any chance I'll overload the 5 volt circuit if I turn the resistance down too low? Pete in Hyder We're all here 'cause we're not all there. |
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djuqa Guru Joined: 23/11/2011 Location: AustraliaPosts: 447 |
50' is really pushing it that is what Rs-422/Rs-485/RS-232 (50' is even too much for RS232)/ Rf links are for. Digital TTL/CMOS level signals are not designed or capable of long distance usage. Use another mazimite/duinomite/arduino/picaxe as a remote display controller & interlink it to the main module Investigate using these modules especially the ones with SPI http://www.futurlec.com.au/RadioModules.jsp VK4MU MicroController Units |
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| Buchan Newbie  Joined: 25/09/2011 Location: AustraliaPosts: 12 |
G'Day Folks, I made a GPS using a Z7001 LCD from Altronics and a Pololu GPS engine GPS-002 from Ocean Controls. This is used in both my tractor and Ute. Works fine - only wanting to log (at the moment) hazards and boundary locations. Also used to log soil sample test sites. Both LCD and GPS program parts were as per Geoff's code, with minor alteration to interface each together. The LCD.BAS is connected as per the layout shown in LCD.PDF. Connection being by using wires from some CAT4 cable and F-F jumpers from the MM to a little bit of Vero. Power supply is from cig. lighter socket (finally useful for something), using a little bit of Vero to make a p/s almost like Geoff used in the Car GPS. Black squares on the LCD when wired as shown, can also mean a 'space'. Regards, Doug, Even farmers need computers. |
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| pcaffalldavis Senior Member Joined: 17/10/2011 Location: United StatesPosts: 187 |
Those wireless data links look pretty nice. I'll have to try learning about those. I'm so back and forth on these LCD's it is driving me crazy. It worked as digital for a while today, then stopped working again. I don't know if it is voltage related or what. I have another bit of glitch that might help give a clue. I have real time clocks on the MM I'm using, and I always have the autorun.bas program get the date and time from the RTC. Usually booting works just fine, and this clockread program which has been renamed autorun.bas works. Then at the end it calls and runs the LCD test program. Sometimes when I boot with the MM 26 pin cable connected to my boiler board the MM fails to load the date and time saying the date$ is wrong or there is an error in a line of code. If I disconnect the ribbon cable and reboot this NEVER happens and the date & time loads just fine. That makes me think there is a voltage problem when the secondary boiler board is connected to the MM. Does that sound right or possible? Other times I have no trouble booting the MM with the secondary board connected. There are no shorts on the Boiler Board, but I wonder if the initial voltage draw to all the mosfet circuits, temperature sensor circuits and ribbon cable to the LCD draw just too much power. Sometimes it is pretty cool in the workshop, as in not really warm, but I don't know if that would affect the LCD or MM. This is just so puzzling. When the LCD stopped working again today using digital Setpin 8, I replaced the 10 K resistors I had removed with 5K resistors and changed it back to Open Collector. It did not work that way. Guess it really does need 10 K resistors, and when they don't work 5 K don't either, even with 46" of cable to the LCD. I'm wondering if I'm asking for too much from the MM power supplies, 3.3 and 5 Volt sources. Should I perhaps round up another 5 volt supply and connect it directly to my secondary board? My MM 3.3 volt supply is actually 3.26 volts. The 5 volt source runs around 4.99 volts most of the time. The good news is that I have the 10 Ohm resistors on the board now and all seven MOSFET circuits are working now as are all four temperature sensing circuits. I can now use this Boiler Circuit Board for everything I designed it for, other than the irregular LCD output. I'm beginning to wonder if I should not perhaps just find a way to use a 4.3" TFT as the data display. Might be easier than figuring out what is going on with the 16 x 2 LCDs. I want to thank everyone for their assistance. I'm learning albeit slower than I'd wish. Pete in Hyder We're all here 'cause we're not all there. |
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| rhamer Senior Member Joined: 06/06/2011 Location: AustraliaPosts: 174 |
Having an LCD on the end of 46" of cable is too far. As you are seeing it may sort of work sometimes. The capacitance of the cable is affecting the waveform shape and rolling over the sharp corners. This is bad. You either need to shorten the cable by a lot, or drive it some other way. If you google "serial LCD" you will find there are displays that can be driven serially which will give you longer cable runs. These are either a custom LCD with the serial driver built in, or a plug on backpack that plugs onto a standard LCD like you have. Another advantage of this approach is it only needs 1 data pin to drive it and one line of code to display text. No more mucking around bit banging the init sequences etc. all that is done for you bu the little micro in the backpack. The usually have good cursor control as well so you can set the cursor to an absolute position and write text to that position, without the need to write the whole display each time. Cheers Rohan Rohan Hamer HAMFIELD Software & Hardware Solutions Makers of the Maximite Expander. http://www.hamfield.com.au |
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| pcaffalldavis Senior Member Joined: 17/10/2011 Location: United StatesPosts: 187 |
Sounds good. I've ordered up a serial LCD interface and two TFT screens. One 3.5" and one 4.3". I'm not sure which display I'll prefer when all is said and done. And there is another option for the remote display in the house I think. I have a 16 channel CCTV security system. I might be able to send the MM composite signal into the security system as if it were a camera's signal. I don't know if this will work yet, but if it does that would make the boiler information available anywhere the security images are, which is at every TV in the house, and even over the web! I'll have to try this later. Pete in Hyder We're all here 'cause we're not all there. |
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CircuitGizmos Guru Joined: 08/09/2011 Location: United StatesPosts: 1425 |
I do something like that. Quite convenient. Micromites and Maximites! - Beginning Maximite |
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donmck Guru Joined: 09/06/2011 Location: AustraliaPosts: 1313 |
me2 I have a good quality two channel RF modulator. Feed the CCTV system down one, and cable TV down the other. Any TV anywhere, can pick up everything. CCTV system also feeds to my router, so I can tell if my neighbor has put the rubbish bins out while I am away. 
Cheers Don... https://www.dontronics.com |
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