im program a led blinking into a pic16f877a with portb pin 7 as the output with 250ms delay.
when i measure the output with oscilloscope, then waveform is like a saw,so is possible to make it square wave?
how can it be sawtooth? perhaps there are capacitance issues.. check your circuit's pinouts and make sure it doesn't have any impurity like flux residue, etc.
Is the port TRIS always set to OUTPUT and you are toggling OUT from 0 to1 ?
Are you using a resistor in series with the LED?
Is the Cathode of the LED grounded; or is the Anode tied to Vcc?
im program a led blinking into a pic16f877a with portb pin 7 as the output with 250ms delay.
when i measure the output with oscilloscope, then waveform is like a saw,so is possible to make it square wave?
Just by chance what settings are you using for vertical coupling on your scope? I would venture you are AC coupling to the scope and this is a very slow pulse repetition rate. If the LED is producing nice sharp blinks then you should have good pulses and I would venture you are set up for AC coupling or using a probe in serious need of compensation on the scope. DC couple your signal in your scope settings.