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SparkFun LCD what to put into Vee

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crutschow

Well-Known Member
Most Helpful Member
According to the "Electical Absolute Maximum Ratings" table Vee can be between Vdd-19 to Vdd+0.3.

So if you are applying +5V to Vdd, then Vee maximum values are between +5.3V to -14V. According to the "DC Electrical Charcteristics" table typical Vee would be -3V to -12V for Vdd=5V.
 

excetara2

New Member
Almost

**Sorry, meant to make this a new topic, this has nothing to do with the Vee**

OK, I've narrowed down the problem. Using a logic analyzer, I realized that my ENABLE signal is not being pulsed (I believe it has to go from 1 to 0 for the instruction to be executed). In the code that I downloaded, it has these two lines:

#define LCD_E_HIGH (PORTD |= (1<<5))
#define LCD_E_LOW (PORTD &= ~(1<<5))

Then, to set ENABLE high or low they simple just use

LCD_E_HIGH; or
LCD_E_LOW;

Does anyone see a problem with these? For some reason they are not triggering the enable. Or can someone explain what the first two instructions do?

Thanks again!
 
Last edited:

duffy

Well-Known Member
The first one says to OR portD with 1 shifted to 10000, the second says to AND it with the complement of 1 shifted to 10000.

This looks way too complicated for a #define compiler instruction. Assign LCD_E_HIGH and LCD_E_LOW to macros that do direct bit manipulation or bit masks.
 
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