I have an LK202-25-WB as a display only driven by a 16F877A through a Max232 for the RS232 connection running at 9600-n-8-1. The 5VDC power is supplied through the DB9 connector And has worked predictably for about 2 years now. This display is usually just left on 24/7 but has been encountering a problem.
About every 6 months the display itself will no longer respond correctly. Removing the LCD display and connecting it directly to a PC I have been unable to communicate with the device at any speed. Only garbage characters are displayed at best. I have read the manual (several times) and checked the forums and have found similar problems, no solutions.
I can use the reset jumper to make the display fire up at 19,200 and communicate well with the device. Using uProject I can run through with no errors and communicate well. The problem comes with none of the settings will be saved. The only way to get the unit to be responsive at all during power up is to use the Reset jumper again.
any suggestions as to how this could be remedied?
Thanks, Joe...
LK202-25-WB
Hi Joe,
Looks like the first problem you may be having is that manual override is temporary. As soon as you take off the jumper the display goes back to what every settings it was at prior to the override. If you haven't already you'll want to change your baud rate to 19,200 while the display is in override. Take the jumper off and cycle power to make sure that this sticks.
Next, for the larger problem of the display forgetting it's baud rate every 6 months or so, you may want to lock down your display. If it's a newer revision, 3.0, you can check out the data lock section in your manual. You'll want to set and save the data lock to at least 0x10 (8 decimal) to make the baud rate much harder to change inadvertently.
Thanks,
~Troy
Looks like the first problem you may be having is that manual override is temporary. As soon as you take off the jumper the display goes back to what every settings it was at prior to the override. If you haven't already you'll want to change your baud rate to 19,200 while the display is in override. Take the jumper off and cycle power to make sure that this sticks.
Next, for the larger problem of the display forgetting it's baud rate every 6 months or so, you may want to lock down your display. If it's a newer revision, 3.0, you can check out the data lock section in your manual. You'll want to set and save the data lock to at least 0x10 (8 decimal) to make the baud rate much harder to change inadvertently.
Thanks,
~Troy
Troy Clark
Design & Development
Matrix Orbital
Design & Development
Matrix Orbital
Thanks for the quick response.
As for the first approach I've tried this and several approaches to this method and it can accept these settings and communicates very well through a PC. The problem is when you cycle the power ALL settings that were modified disappear and operation reverts back to the same as prior to the reset.
I have not used the data lock approach yet as I am only using this as a dumb display, I will refer to the manual again when I get home tonight. If the settings are not being remembered; would the data lock help?
Question for you, From my observations it appears that the onboard RAM and EEPROM are funtioning properly. It seems as if the flash memory is getting corrupted. First, Is this possible? Second, Can this be corrected?
Also, It is possible (not likely but possible) That I could be getting voltage spikes through my 5VDC switching power supply. I have spent many hours with a voltmeter plugged into the supply line and have recorded no such thing. However I have never observed this problem while logging either. Do you know what the actual Maximum voltage this unit will allow before doing damage of this sort?
Thanks, Joe...
As for the first approach I've tried this and several approaches to this method and it can accept these settings and communicates very well through a PC. The problem is when you cycle the power ALL settings that were modified disappear and operation reverts back to the same as prior to the reset.
I have not used the data lock approach yet as I am only using this as a dumb display, I will refer to the manual again when I get home tonight. If the settings are not being remembered; would the data lock help?
Question for you, From my observations it appears that the onboard RAM and EEPROM are funtioning properly. It seems as if the flash memory is getting corrupted. First, Is this possible? Second, Can this be corrected?
Also, It is possible (not likely but possible) That I could be getting voltage spikes through my 5VDC switching power supply. I have spent many hours with a voltmeter plugged into the supply line and have recorded no such thing. However I have never observed this problem while logging either. Do you know what the actual Maximum voltage this unit will allow before doing damage of this sort?
Thanks, Joe...
Clark wrote:Hi Joe,
Looks like the first problem you may be having is that manual override is temporary. As soon as you take off the jumper the display goes back to what every settings it was at prior to the override. If you haven't already you'll want to change your baud rate to 19,200 while the display is in override. Take the jumper off and cycle power to make sure that this sticks.
Next, for the larger problem of the display forgetting it's baud rate every 6 months or so, you may want to lock down your display. If it's a newer revision, 3.0, you can check out the data lock section in your manual. You'll want to set and save the data lock to at least 0x10 (8 decimal) to make the baud rate much harder to change inadvertently.
Thanks,
~Troy
Joe williams
Hello Joe,
While you have manual override on, remember to save all the settings. It is easy to forget this step. Remember to save the baud rate, contrast and backlight settings. Cycle the power without the manual override jump and check if the settings stick.
As per locking the display's settings, try setting bit 4 of Data Lock. Make sure though that before you do this, you have all the settings you want (ie when you have done manual override and saved the settings).
Flash and EEPROM corruption are likely when you run the display at low voltages, or when you have unclean power supply, but you mentioned you have a switching regulator that regulates your 5VDC, so we should be fine there.
While you have manual override on, remember to save all the settings. It is easy to forget this step. Remember to save the baud rate, contrast and backlight settings. Cycle the power without the manual override jump and check if the settings stick.
As per locking the display's settings, try setting bit 4 of Data Lock. Make sure though that before you do this, you have all the settings you want (ie when you have done manual override and saved the settings).
Flash and EEPROM corruption are likely when you run the display at low voltages, or when you have unclean power supply, but you mentioned you have a switching regulator that regulates your 5VDC, so we should be fine there.
Raquel Malinis
Design and Development
Matrix Orbital
Design and Development
Matrix Orbital
Thanks for the assistance in this matter it was a great help along with the documentation. Using the menu features and remember wouldn't save the settings. However http://www.lcdforums.com/forums/viewtopic.php?t=3371 along with the previous tips actually set and retained the Baud rate. It appears as the display communications are working properly! This is a very good thing and leads me to believe I've got some data cable interference going on over here.
A side note however which I noticed is although I can now talk to the display; the other non-text features through uproject don't seem to function properly. This is not such a concern to me as the basic funtionality is working properly. I am figuring this is due to the same problem that corrupted the Baud rate settings, I will try a few things to reset the remaining settings back where they belong then the "Lock" feature sounds like my best layer of protection in preventing this in the future.
Thanks again! Joe...
A side note however which I noticed is although I can now talk to the display; the other non-text features through uproject don't seem to function properly. This is not such a concern to me as the basic funtionality is working properly. I am figuring this is due to the same problem that corrupted the Baud rate settings, I will try a few things to reset the remaining settings back where they belong then the "Lock" feature sounds like my best layer of protection in preventing this in the future.
Thanks again! Joe...
Joe williams