Jee Labs Café/ lab/ LCD Plug (v1)
  1. Configuration
  2. Header Pinouts
  3. Design Info
  4. How to Get It
  5. Related Weblog Posts

The LCD Plug is a small board which is designed to sit piggy-back on an HD44780-compatible LCD display with 16-pin connector - the plug is based on the same MCP23008 as the Expander Plug:

lp1.DSC 0722.JPG.jpeg lp1.DSC 0721.JPG.jpeg

The backlight can be controlled via software to reduce power consumption. A BC817 is now used as switch, it can drive up to 500 mA for the backlight. The driver software and an "lcd_demo" example sketch is included in the Ports library.

An I2C bus running at 3.3V is used for I/O, with all the power and signal lines brought out to to both sides of the board to allow daisy-chaining with other I2C-conformant boards.

Configuration

The I/O expander chip on this plug is set to respond to I2C address 0x24.
The logic supply voltage has to be jumpered to either the PWR or the +3V pin.
The backlight voltage has to also independently be set to either PWR or +3V.
There is room for a backlight current limiting resistor, or use a jumper to bypass it.
And lastly, there is a mini trimpot on the board to adjust the LCD contrast level.

For the LCD from Jee Labs, use logic level set to PWR or +3V (depending on which type of LCD you got, see below), backlight set to +3V, and a solder bridge to short out the optional backlight current limiting resistor.

If appears that some LCD's may have pins 15 and 16 reversed: this board assumes that - is pin 16 (the outermost one) and + is pin 15. If that's not the case, omit the LIGHT jumper and current limiting resistor to detach both pins from the circuit. Then patch them up to match your LCD display.

The pins marked SW (switch) are tied to a spare I/O pin and ground, they can be left disconnected.

Note - As of June 2010, the 2x16 LCDs from Jee Labs are 3.3V units. These have a "33V33" suffix on the label. When you see this label, use +3V for both logic level and backlight:

DSC 1522-label.jpg

Note - It is sometimes hard to get the LCD display to show proper characters. In 9 out of 10 cases, this is due to the trimpot not being set properly - you have to find the exact position at which the characters are readable. Too far one way and nothing shows up, too far the other and all the characters will show as black blocks. Somewhere in between, you get a properly readable display. You can use a mirror to see the display while slowly turning the trimpot with a small screwdriver.

Header Pinouts

lp1. 00000319.png

Design Info

Dimensions: 21.1 x 41.9 mm
CadSoft EAGLE design files: jlpcb-043.pdf / jlpcb-043.sch / jlpcb-043.brd.
This plug can be operated at 5V as well as 3.3V.

This board uses the conventions of a JeePlug and can be used with the ports on a JeeNode. It can also be used with other boards and MCU's, if you hook it up properly and adapt the interface code for it.

How to Get It

http://shop.jeelabs.com/products/lcd-plug

Related Weblog Posts