Project update ...
I like to point out that the 4x20 is, of course, larger than the standard 16x2 LCD that fits on this shield. I used
a 18 pin female 0.10 space socket on the shield board to mate to the larger 4x20 LCD. Some nylon spacers and hot glue wasused between both boards for support. Note: the larger LCD blocks the tact switches from being used!
Since the tact switches were not accessable when using the panel mounted larger 4x20 LCD with the shield, I used Adafruit's tact switch navigation joystick to supply the proper inputs to the shield. On the back of the shield, I installed the I2C 4.7K pullup resistors, in case they had to be changed for different configurations and I also soldered the LCD contrast pot on the back so I could easily adjust the LCD contrast. As you can see, I hacked this shield to death for to meet our project's special requirements but in doing so brought up a new product idea for Adadruit. A standalone RGB LCD controller with tact "joystick navigation. Another addition would be to add an I2C digital pot or PWM to control the contrast from the user's microcontroller?
BTW ... Adafruit and especially Limor Fried would be extremely proud of our project because we used over a dozen high tech parts from Adafruit without which our project would never be completed!
Here is a short listing ... Adafruit plug ...
Alpha Clock Five kit https://www.adafruit.com/products/620
LCD I2C shield with 5 tact switches replaced by tact joystick (hacked or modified) http://adafruit.com/products/715
RGB backlight negative LCD 20x4 (modified to fit 2x16 LCD shield) https://www.adafruit.com/products/498
Ultimate GPS (modified-remote mounted fix LED) http://adafruit.com/products/746
+5 VDC to 3 VDC level converter (for I2C LCD) http://adafruit.com/products/757
INA219 High Side DC Current Sensor Breakout http://adafruit.com/products/904
Electrc IMP SD WiFi card (modified for network time and status) http://adafruit.com/products/1129
Tact joystick (modified for LCD display) https://www.adafruit.com/products/504
CR2032 battery holder(s) (Standardize battery holder for all lithium backups) https://www.adafruit.com/products/653
Spring loaded terminal blocks for 5 V bus bar https://www.adafruit.com/products/1074
Protoboard for 5 V bus bar https://www.adafruit.com/products/589
Panel mount power connector 2.1 mm https://www.adafruit.com/products/610
Teensy 3 ARM Stamp http://adafruit.com/products/1044
In our "DoomsDay Atomic Alpha Clock Five Project" we used a Ultimate GPS, a WiFi Electric IMP (network time), a WWVB Atomic radio receiver, two precision TXCO real time clocks (+- 2 PPM SPI DS3234 and I2C DS3232) and two microcontrollers - (Teensy 3 ARM stamp & Arduino 328P clone). We then use the three precision clock sources (UNIX seconds) to drive or sync to the Evil Mad Scientist huge, very bright, "Alpha Clock Five" 2.5" clock display.
Project link....http://forum.pjrc.com/threads/17369-Doo ... e-Teensy-3