2018-04-06 11:19 PM
Hello, So I am using a STM32L100C-DISCO to display some numbers on an LCD display, I am using the LSI as the clock source. My program works fine for a couple of hours, but if I de-power then power-on the board, the LCD booster circuit does not turn on. I thought this might be a board malfunction because of me blowing it up, but everything else works. I then bought another of the exact same board and tried it. Does the exact same thing as the first board. But now if I leave the first board unplugged for a couple of hours the LCD booster circuit on the that powers on, and my program works fine. I tried this with the second board but with it still plugged into the LCD but with no power, and the booster circuit wont start up. I have no explanation for this. I am using AC6 with the latest firmware.
thanks
#lcd #stm32l1 Note: this post was migrated and contained many threaded conversations, some content may be missing.2018-04-07 03:21 PM
What LCD? What booster circuit? Why do you think this is STM32-related?
JW
2018-04-07 05:59 PM
sounds like the LCD backlight,
do you have a dimmer function ?
2018-04-08 12:01 AM
The LCD booster circuit is meant to control the contrast of the LCD, it also acts as the power supply for the LCD. But I dont have a function for this, the contrast is automatically set in the CubeMx setup
2018-04-08 12:02 AM
because the LCD booster circuit is inside the stm32 microcontroller
2018-04-08 02:55 AM
You mean the Step-Up converter mentioned in RM0038 16.4.5 Voltage generator chapter?
There is no LCD on the STM32L100C-DISCO so it's something you've connected to it. What display is it and how did you connect it?
JW
2018-04-08 03:22 AM
Hello, I think so?, the manual I have say the built in LCD voltage generator, the LCD im using this:
https://docs-apac.rs-online.com/webdocs/144d/0900766b8144dacf.pdf
, I have just connected all pins from the LCD directly to the board, do I need a resistor?thanks
2018-04-08 03:42 AM
Oh, but that's a 5V display... How did you connect the COM pins?
JW
2018-04-08 03:45 AM
I connected the com pin of the LCD directly to the com pin of the board, I assumed that the power was supplied from the com pin
2018-04-08 04:06 AM
That's correct. However, given the display is 5V according to its datasheet, I still wonder how comes it works at all, given STM32L1xx's output voltage is max. 3.6V.
You are supposed to have a capacitor connected to the VLCD pin, have you? See datasheet for details. Then measure voltage on that pin. Better yet, get an oscilloscope and observe the waveforms on COM and a 'lit' SEG pin.
JW