User avatar
joan
Posts: 14843
Joined: Thu Jul 05, 2012 5:09 pm
Location: UK

Re: Debugging a I2C 20x4 LCD

Sat Oct 01, 2016 10:15 am

That doesn't look like a MCP23017.

To double check I suggest you remove the power and ground wires from the chip and then replace to make sure the chip is reset. Then try the test once more.

User avatar
dentex
Posts: 180
Joined: Sun May 20, 2012 7:58 am
Location: Italy
Contact: Website

Re: Debugging a I2C 20x4 LCD

Sat Oct 01, 2016 10:27 am

joan wrote:That doesn't look like a MCP23017.

To double check I suggest you remove the power and ground wires from the chip and then replace to make sure the chip is reset. Then try the test once more.
Done. Same result (after this test, the LCD remains with no back-light).

On the I2C back-pack, the IC is marked as PCF85740T, if may help.
One of my projects with the Raspberry Pi:
--------------------------------------------------------
(Raspberry) Pi Aquarium Controller: https://github.com/dentex/piac

User avatar
dentex
Posts: 180
Joined: Sun May 20, 2012 7:58 am
Location: Italy
Contact: Website

Re: Debugging a I2C 20x4 LCD

Sat Oct 01, 2016 1:50 pm

SOLVED!!!!

It was a stupid "hardware" issue...

I was checking every pin on the PCF8574T to see where each LCD pin was connected to... and I noticed that although a track from IC pin 9 (P4) seemed to be connected to the LCD's pin 11 (D4), the IC pin was actually slightly bended upwards and it wasn't touching the PCB. I soldered it properly and it worked. Almost EVERY library I tried actually worked. :evil:

I would like to thank everyone who helped me to "debug" this guy... This is really a great community :)
I'm sorry I didn't notice this issue before and if I have possibly made you waste some time.

Thanks people!

Image
One of my projects with the Raspberry Pi:
--------------------------------------------------------
(Raspberry) Pi Aquarium Controller: https://github.com/dentex/piac

Return to “Interfacing (DSI, CSI, I2C, etc.)”