CFAH4004A-YYH-JP Voltages

[glsdean]

I'm troubleshooting reasons for being unable to initialize a CFAH4004A-YYH-JP LCD. Would a Forum member or Tech Support please tell me what range of voltages I should expect to be delivered to the CFAH4004A Enable, Data, R/S and R/W pins for the LCD to function properly. Thanks for your help.

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[cosmicvoid]

According to the data sheet, a 1 state must be higher than 2.2 volts, and a 0 state must be lower than 0.6 volts.

 

[CF Tech]

For starters, set Pin 3 (Vo) to about 1 volt, which will make Vlcd 4 volts (for a 5v system). If the display is initialized the text will be visible at that setting.

 

[glsdean]

Measured Voltages

Vdd going to the LCD is about 4.9 VDC. Voltage at E1 and E2 is about 0.76 VDC. DB4-7 voltages are approx. 1.25 VDC. Voltages for R/S and R/W are about 1.54 VDC. Are these values typical?

 

[cosmicvoid]

If you are measuring when there is signal activity, then you are reading the average voltage based on the duty cycle of the activity, and those voltages are "OK" but meaningless.

If you are measuring with the program halted, and things are static, then those voltage are not good, and not typical.

 

[glsdean]

Actual Voltages

Actal measured voltages (VDC) at the LCD connector were as follows:

DB7 = 1.02
DB6 = 1.48
DB5 = 1.33
DB4 = 1.30
E1 = 0.74
E2 = 0.74
R/S = 2.86
R/W = 0.00
Vo = 0.00
Vss = 0.00
Vdd = 4.94

I can only assume that thse voltages were occuring while the program was running. Can you tell me what you mean by the measurements being OK, but meaningless? Is there something else I should be checking to see that I am getting "good" output from the microprocessor to the LCD?

 

[cosmicvoid]

Can you tell me what you mean by the measurements being OK, but meaningless?

If you are measuring with a VOM, and the state of the pins is changing rapidly, then the voltage is meaningless because the meter is integrating the input over 10's or 100's of milliseconds. I suppose if all the voltages were 0v or 5v, that might be meaningful (as in... things aren't changing state when the program runs).