ATMEGA32U2 connection problem –
12-04-2010,07:48 AM
Hello PS freaks, I am having problem with my self-made dongle based on ATMEGA32U2 MCU. I have soldered and attached everything according to my_project.zip (schematic,board). All the stuff looks pretty good, but...
After connecting to PC nothing happened... PC do not recognize any USB device. In HW manager USB port looks like there is no device connected...
Of course I have performed the bootloader start (press and hold WHB, press RESET, release RESET, release HWB). And nothing...
So I have started the measurings...
The pins: AVCC(32), UVCC(31) and VCC(4) are connected to +5V (correct value)
pins: UGND(28) and GND(3) are connected to GND potential... (correct)
pin UCAP (27) shows 3,3V on it. (correct value)
pin 24 - RESET is after start on +4,71V... (correct value)
pin 13 - HWB is connected to +5V via pushbutton "HWB"... (correct value)
All the ports (PB,PC,PD) are on something around 70-100mV. (should be correct for unprogrammed MCU).
BUT!!! Pins DATA- and DATA+ (30,29) have both 0(zero)Volts!!! I think there should be bus voltage (3,3V). So it looks like USB upstream and downstream ports are turned OFF! (Thats just my oppinion). I will try to catch some signals after connection on oscilloscope, to make sure, that there is no data transfer.
Now I am bit confused, what is wrong... So I kindly ask anyone, Who has some idea how to solve this fu*king problem!
THANKS
EDIT:
Oscilloscope meassuring has shown what I did expect... no data transfer on USB bus...
The main problem was really value of coupling C for X-TAL!!!
I have replaced them vith 18nF and everything works!!!
Thank you for advice!
Take care Alfa1962