Had a slight problem with connecting a 16X2 Character LCD to a Pro Micro board. Basically as originally wired, it was only displaying one line of characters, and not responding to any of the control commands such as clear() home() etc.
It seemed to me that the problem was with the register select line RS, as there was some expected characters being displayed.
So I moved the RS signal from D2 to D9 and it now works fine.
My suspicions are that the D2 pin is either being used for something else, or requires an external pull up because it also serves as the I2C SDA pin.
Just wondering if this is expected behaviour, and if so where is the best place to find out more detailed info on the pin assignments for the Pro Micro boards.
For info, happens using Arduino 1.5.8 natively, and as a visual Micro plugin for AtmelStudio
My suspicions are that the D2 pin is either being used for something else, or requires an external pull up because it also serves as the I2C SDA pin.
It's possible that your original connection to pin D2 was not up to par. Just about all of the pins on the processor serve a dual purpose but if you aren't using any of the alternate functions of those pins there will not be any problem using them for the LCD.
I think my connections were fine. I'd made two prototypes with soldered joints. Neither worked until I changed from D2. Thats not to say there isn't a problem with the PCB or soldering to the micro. Will have another go later, and look at some signals on scope.
My suspicions are that the D2 pin is either being used for something else, or requires an external pull up because it also serves as the I2C SDA pin.
There's something else wrong here.
The alternate function for the Arduino D2 pin which is Atmel Port D2 is INT0.
The SDA pin is assigned to Atmel Port C4 which is the Arduino A4 pin.
The Arduino A4, A5, A6 and A7 pins are inboard (not on the outer edge of the pc board) and A6 and A7 are NOT general purpose I/O pins unlike most of the other pins.