RE: [tracker2] Tracker2 with LCD display
- Hi Steve,
PIN Symbol Level Function
1 VSS - GND(0V)
2 VDD - Supply Voltage for Logic(+5V)
3 V0 - Power supply for LCD <-- A pot between 5V and GND with the wiper connected to PIN 3 works well. The contrast can be changed as temperature changes.
4 RS H/L H: Data; L: Instruction Code
5 R/W H/L H: Read; L: Write
6 E H/L Enable Signal
7 DB0 H/L <-- not used
8 DB1 H/L <-- not used
9 DB2 H/L <-- not used
10 DB3 H/L <-- not used
11 DB4 H/L
12 DB5 H/L
13 DB6 H/L
14 DB7 H/L==================
15 A - Backlight Power (+5V)
16 K - Backlight Power (0V)These connections should have a current limiting resistor added in series. At least on the ones I have used in the past. Actually a pot here helps to adjust the brightness as needed with a series fixed resistor.
I added a portion of my schematic. I don't show the VO circuit or the backlight circuit either. I have a simple pot for VO. I think my pot is 20K. I am thinking my data sheet actually had a current listed for the VO pin.I usually control the backlight with PWM (contrast too) but it seems a bit overkill here.You will want to limit the current to the backlight LEDs.The Vf is 4.2 for the Y-G version.So5.0V - 4.2Vf = 0.8V0.8V / 0.180A = 5 ohms (rounded 4.44 to 5)A 5 ohm resistor in series with the backlight LEDs should keep it safe.The Vf is 4.0 for the WHITE version.So, 5.0V - 4.0Vf = 1.0V1.0V / 0.030A = 33 ohmsA 5 ohm resistor in series with the backlight LEDs should keep it safe.So depending on which model you find, either a 5 or 33 ohm resistor should keep the backlight in action.In you want to dim it further, then a pot in series with your other resistor can decrease the current (light output) without allowing you to overdrive the backlight.I also added pictures showing my additions to the Tracker2. And there is one of the LCD in action.Best regards,Fred
> - display outputs gibberish characters on lines 1/3 when T2 writes to it. But I never see gibberish on lines 2/4Power up sequence? What Power up sequence? Ohhhhhhhhh, you mean *that* power up sequence.
Fred tells me the following in an email "The LCD has a particular startup sequence and this will only be done at the T2 startup."
Whereas, I took the WIKI quite literally "No configuration is necessary. The standard Tracker2 firmware will begin using the display automatically. "
So, I just plugged it in, hot. What a newbie mistake!
> -I put an SPST switch on +5v input (pin 15 on the mono8) andBad switch - still delivering +3.9V power in the OFF position
> here's the really weird part. When I turn on the switch, the display and the backlight LEDs come on. When I turn off the switch, the LEDS remain on, but dim down a bit.