LCD backlit no text

[msmmark]

I finished the build on the V2.1u and conducted the tests. The resistance on the vin gnd I believe is about 5K the resistance vcc to gnd is infinite. when powering the unit with 24V transformer I get 5 volts at VIN and 3.3 volts at VCC give or take a tenth.

powering the unit with USB the LCD back lights but no text. I have checked all the pins going to the lcd all show continuity. I have reinserted the lcds and they are all correctly inserted with no bent or ascue pins.

Please help

Thanks

[Ray]

My suggestion is to first check if the microcontroller is up running. There are a couple of things you can do to verify this, for example,

– plug the unit into your router and power it on, wait for a couple of minutes, does it get an ip address (since LCD is not working, you need to check this on the router’s configuration page, typically under Client List).
– press and hold pushbutton B2 while plugging in the USB cable, then release B2 after 1 to 2 seconds after USB cable is plugged in — does the screen remain off? At this time it should appear as an USBasp device on your computer.

If any of the above succeeds, it means the miccrocontroller is up running and the problem is most likely in the LCD. You can send an email to [email protected] to arrange for a replacement. If the above fails, you may want to recheck if the microcontroller is inserted correctly, whether the crystals are soldered correctly etc.

[msmmark]

Ray,

I received the new LCD display and tried it. The problem still persists. the unit LCD is backlit but no text in the display. What next.

Thanks

[Ray]

This means the problem is not in the LCD, it’s somewhere else. Perhaps the LCD contrast value has been changed for some reason. Try to perform a reset: turn off controller, press and hold button B3 while plugging in a USB cable (or power the controller on), do you see any display text? If so, click B3 until you see the ‘Reset All?’ option, and click B1 or B2 to select Yes. Then press and hold B3 until the unit restarts.

[msmmark]

Ray,

Doing this there is no text displayed on the LCD. I have run through all the prescribed tests again. I get the same results. I am wondering if the infinite resistance VCC to Gnd could be the cause. Could there be a broken trace on the pcb. or a solider joint not making contact.

I have attached to router and get an ip address assigned and am able to access the web interface page of the open sprinkler unit.

I have attached screen shots of the the router device page and the open sprinkler main page for your reference.

Thanks

sorry could not attach PDF files. can email screen shot if you need them

Thanks

[Ray]

Not sure what else to try. Clearly the microcontroller and Ethernet controller are both running fine, so VCC is clearly ok. The infinite resistance should be ok (the reading may vary depending on the multimeter, as long as the voltage is about 3.3V it’s fine). The LCD you received has been tested and verified to work.

The LCD backlight and contrast are each controlled by a microcontroller PWM pin. The fact that you see backlight on means at least one of the PWM pins is sending signal correctly to the LCD (otherwise the LCD will remain dark). So this leaves some of the other LCD pins to check. One thing I suggest you do is to measure the voltage on each of the LCD pins: if you look at the LCD, there are 16 pins, labeled VSS, VDD, VO etc. VSS is ground. Could you measure the voltage from each of the pins 2 to 15 to ground, and write down the voltage value? This way I can compare to the reference voltage and tell which pin is having a problem.

[msmmark]

ok I proceeded to check the voltages on all the pins as asked. Even though I had checked continuity of all the pins earlier and verified contact of the pins I pulled out a magnifying glass and looked at the pins on the connector and found several broken solider joints. I re soldered the connector and like magic it now works.

Thanks for you help in getting this working.

I now have two LCD displays would you like me to return one? Thanks for the assistance.

Mark

[Ray]

OK, glad to hear it’s fixed now. You can keep the extra LCD, no need to return it.

[Author]

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