On Mon, Dec 7, 2009 at 7:22 PM, Cristiano Cesaretto wrote: > Hi all. > I was wondering if someone has an advice for a driver for a 7 segments > display. I need to be able to adjust the brightness of the display "in > software", with a command. The display drivers I have found so far expect an > external resistor to set the brightness level. > > Other approaches are ok, if I can get the same result. I also have enough > pins to connect directly avery single segment of the display, if this helps. The way to go would be to use a PWM signal to strobe the LEDs at a frequency of 100Hz or so, with a duty cycle proportional to the desired brightness. You can accomplish this either by driving a transistor in the common anode/common cathode of the LED display, or by using AND gates to AND the PWM signal to the drive inputs of each of the segments. If you have multiple digits that you're looking to multiplex, it gets more interesting. I've used a NAND gate that fed four logic-level FETs connected to each of four common cathode LED digits, so that each digit could be turned on/off at will and also brightness-regulated via the PWM. -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist