LCD gets blank when phonograph starts

wmarkow / arduino-hifi

A small HiFi system built with Arduino

MIT License

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LCD gets blank when phonograph starts #1

Closed wmarkow closed 6 years ago

wmarkow commented 6 years ago

A strange issue. How to reproduce:

attach the power source from main segment to phonograph segment (s0 phonograph is powered from the 12V from main segment)
turn on the main power supply -> LCD works nice and displays everything correctly
switch on the phonograph by moving the needle arm to the right. The phonograph will be turned on by internal switch (which is attached to the needle arm).
the phonograph's motor starts and the turntable is doing its job but the LCD in main segment gets blank. The main segment seems to be responsive to user inputs; all the controls are working (volume for example); just the LCD is totally blank.

wmarkow commented 6 years ago

It is something related to the power supply. When the phonograph's motor starts it needs some power at the beginning phase. Probably the voltage drops for a while in the main segment and the LCD gets restarted or something similar. It looks like Arduino is not restarted so the LCD is not initiated again.

wmarkow commented 6 years ago

I did a test and I was calling LCD begin() method every 5 seconds. It helps to recover from the strange case.

wmarkow commented 6 years ago

I'm not going to call LCD begin() every X seconds. It would be good to find out if something "bad happen" with the display and then perform reinit on LCD.

I'm using the new-liquidcrystal library.

wmarkow commented 6 years ago

According to this HD44780 documentation, it is possible to read some data from the LCD. I'm using I2C port expander to interface the display. The new-liquidcrystal library doesn't offer a method to read something from the display but I have managed to do this. Please take a look at my forked new-liquidcrystal branch. I have introduced a new method to get character at specific LCD's location (row and column). When the specific character at specific location is blank (but it shouldn't be blank - because I expect some text to be written there) I know that something happen and the screen is blank. Then I perform the LCD begin().

It works fine - for now.

wmarkow commented 6 years ago

I have reported an improvement new-liquidcrystal issues 79.

I know that my solution is just a workaround. I will try to improve the power supply by adding some capacitors.