Objective Development Forums

I'm a beginner in micro-controller and now i'm trying to get vusb working with atmega8.
I used a 12MHz crystal with two 27pf capacitor to supply the clock.
For the circuit of D+ and D- , i found many complex example in net. As i understand that the purpose is to make 5v to 3.3 volt, i used this shortcut.
[D+ from MC]---[68 ohm resistor]---[connection to usb D+]---[150 ohm resistor]---[ground]
same for D-, so 5v coming from microcontroller that become approx 3.4v spliting from 68 and 150. Is that ok ?
Now problem is when i connect it to pc nothing happens.
lsusb and dmesg dont show anything. What to do ?

I wont get in to the ohms law of it all here but I will tell you this. atmega8/88/128/328 all have to have a "perfect" voltage. For example the 128/328 will not work with anything but 1/2 watt diodes. So my advice is try it correctly first, then play with it.

That won't work, since the data lines are pulled up or down. If you are not comfortable with the hardware, I recommend to start with some simple working hardware, such as the one I posted at viewtopic.php?f=8&t=6848

sarim wrote:I'm a beginner in micro-controller and now i'm trying to get vusb working with atmega8.
I used a 12MHz crystal with two 27pf capacitor to supply the clock.
For the circuit of D+ and D- , i found many complex example in net. As i understand that the purpose is to make 5v to 3.3 volt, i used this shortcut.
[D+ from MC]---[68 ohm resistor]---[connection to usb D+]---[150 ohm resistor]---[ground]
same for D-, so 5v coming from microcontroller that become approx 3.4v spliting from 68 and 150. Is that ok ?
Now problem is when i connect it to pc nothing happens.
lsusb and dmesg dont show anything. What to do ?