The Graphics Board lets you create a compact assembly with a 64x128 graphic LCD and a JeeNode (or JeeNode USB, or JeeSMD). Ports 2 and 3 are brought out to attach a variety of additional plugs.
The backlight resistor (R1, 100Ω) sets the display draw to 6 mA on 3.3V and 19 mA on 5V. Adjust the value for different fixed backlight levels.
This board is designed for the JeeNode v5 or newer. If you have a v3 or v4, you will have to mount the two left-hand caps differently because the ATmega is in the way. This does not apply to the JeeNode USB or the JeeSMD.
> The Graphics Board is powered directly from the PWR pin. This means you should restrict the power range to 3.3 .. 5.0V.
> The JeeNode can tolerate higher, but not the Graphics Display.
There is one solder jumper, which determines how to supply power to the backlight: middle-to-P is the default, and drives the backlight from the PWR voltage. Use middle-to-I to connect the backlight to IRQ instead - this lets you control the backlight via software (including PWM dimming). No jumper is backlight off.
The current kit uses ceramic capacitors for a better fit on the PCB, not the cylindrical electrolytics used previously (as in the top right picture above). When constructing the kit, you can ignore the polarity (+/- board marks) with the ceramic capacitors, they work fine either way around.
For the Ports, FTDI, PSIX, and SPI/ISP headers, see the JeeNode pinouts.
The 20-pin graphics connector details can be found in the schematic, see below.
Note that the display needs to seat firmly into the long header (the other edge pins/headers are dummy for location only).
The signals are high impedance/low current so be careful to clean the pins well and check for straightness before inserting evenly.
Dimensions: 67.1 x 51.5 mm
CadSoft EAGLE design files: see below.
The optimum contrast for the display depends on the supply voltage and device to device variation. This can be an issue on the JeeNode USB for example, since its PWR rail is not 5v.
The default setting (defined in the cpp file) is usually close to optimum for an accurate 5.0v supply.
If you see an uneven display with embedded vertical ‘black bars’ similar to the example shown below, the contrast setting needs to be higher.
Change from the default with the GLCD library call glcd.begin(set_contrast_between_0x15_and_0x1A) e.g.
How to Get It¶
Related Weblog Posts¶
- 2010-11-15 - Meet the Graphics Board
- 2010-11-16 - Assembling the Graphics Board
- 2010-11-17 - Room Node display
- 2010-11-19 - Speedier graphics
- 2010-11-20 - Indoor temperature, etc.
- 2010-11-22 - [The obligatory clock…](http://jeelabs.org/2010/11/22/the-obligatory-clock…/)
- 2010-11-23 - 100 KHz DSO
- 2010-11-25 - 2-channel Logic Analyzer
- 2010-11-27 - GLCD on battery power
- 2011-01-05 - GLCD library
- 2012-01-24 - The PWR vs the +3V pin