Mega 2560, UNO, TFT and AM2315C

Other Hardware Displays
1

I have an issue moving a project from a Mega 2560 to an UNO.

I have an ILI9486 TFT display on a Mega 2560. I also have an AM2315C temperature/humidity probe with SDA and SCL connected to the relevant pins located near the USB connector. My sketch uses LCDWIKI and Adafruit_AHTX0 and the project works perfectly. The values from the sensors are displayed correctly on the TFT.

To move to the UNO I uploaded the same sketch, connected the same display and connected the sensor SDA and SCL to pins A4 and A5. Now the problems start. The display starts up OK but goes blank (white) when aht.getEvent(&humidity, &temp); is called. The sensor is working fine as seen on the serial monitor. Only the display is blank.

If I run the supplied TFT test sketch, the display works fine even with the AM2315C sensor still connected. Only when aht.getEvent(&humidity, &temp); is called does the display not do what it is supposed to do.

I have tried this on another UNO with the same result.

Is there such a huge difference between the Mega2560 and the UNO that would cause this?
Any guidance would be appreciated.

2

Can you post a link to the specific display that you are using?

Look at the back of your display and see if the A4 pin is labeled LCD_RST or similar, indicating that A4 is used for the display Reset pin. If that is the case, there is a conflict with the I2C SDA pin on an UNO.

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Hi and thanks. Yes A4 is marked LCD_RST. There is also a dead-short between A4 and SDA and A5 and SCL so that is the problem. It appears that to use this TFT with a I2C device the UNO board is not suitable. However, I may have found the answer elsewhere on this forum that modifies the TFT to make it work by snipping the LCD_RST and pulling it up with a resistor. This I will try. 3.5" TFT LCD ILI9486 problems

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The modification to the pin on the display shield was what I was going to suggest, although I make a 90 degree bend to fold the pin under the display instead of snipping it off.

Be careful to initialize the display before initializing the I2C bus.

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