vusb atmeg8 not detected in pc

[sarim]

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 ?

[ulao]

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.

[xiangrui]

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

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 ?