Re: ic2 display problems #arduino ??? #arduino
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Bill KF7YXSThere are a number of different I2C libraries. The word "different" is key because some function
calls are definitely different. Beauty and curse of libraries is that there are so many different ones
that claim to serve the same purpose.
Analog Pins A4 and A5 seem to be normal for I2C interfaces. The Atmel datasheet for a Mega-328
shows that A4 and A5 connect internally to the TWI (2-Wire Interface) circuitry.
However, there are exceptions where the TWI interface is not available. In those cases you may
have to select a pair of digital pins and write your own bit-banging code to do the TWI protocol.
An I2C interface usually requires 4.7K resistors as pull-up on the SDA and SCL leads. If you look at the
internal schematic for an OLED TFT display you will see that it only has pull-down current devices and no
pull-up components. I fought with this for several days until I finally figured it out. Enabling pull-up
function on the Arduino leads apparently is not adequate. After adding the 4.7K pull-up resistors my display
If you want to have both LCD and TFT displays active it might be worthwhile to turn off the backlight on that
LCD when it is not needed. This will decrease the amount of current drawn by that display.
On Thu, Jun 14, 2018 at 4:17 PM Bill Watkins <kf7yxs@...> wrote: