Hi Joep,
Joep Suijs wrote: > > 2009/4/5 Rob Hamerling <[email protected]>: >> I tried a 16f876A: works! But the maximum lighting with PWM is much >> darker than when I feed pin 15 of the LCD directly with 5V (via a diode >> to het approx 4.3V). I don't know how much mA backlight draws. I >> currently feed it directly from pin_C2, but I probably need a transistor >> or mosfet. > A backlight might well take 100mA, way to much for a PIC pin to > supply. It can make a start, but don't forget to add a resistor to > limit te current. > When you use a transistor, but a resistor in the base circuit, but the > backlight can do without (or one of 10E). I changed my circuit w.r.t the backlight as follows. Pin 15 of the LCD is connected to +5V with a 1N4148 in series. Pin 16 is (via a jumper) either directly connected to ground or to the drain of a BS170. The gate of the BS170 is connected to pin_C2 (CCP1) of the PIC and its source to ground. With a 16f876a the text on the LCD is as expected "Backlight test.", and backlight on/off and fading in/out is clearly visible. Maximum LCD backlight luminosty is about the same as when pin 16 is jumpered directly to ground. However with a 16F886 the LCD text is something else, and backlight is permanently on. The difference in the sources is only the PIC type. As I said, when I do not use the backlight lib the board including LCD works find with both PICs. So it seems to me that either the PWM lib or the backlight lib is the bad guy. > I don't know what 'enhanced pwm' is. Is it a feature of 16f886? Have a look in the datasheet of the 16F886. > And does the pwm test programs of Seb run okay on this chip? No (I tried Seb's test program on this board with the LCD backlight as the 'LED'!). Regards, Rob. -- Rob Hamerling, Vianen, NL (http://www.robh.nl/) --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "jallib" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/jallib?hl=en -~----------~----~----~----~------~----~------~--~---
