K8055 not responding to usb connection

Kits PC Related Projects
1

hello

2006 i bought a K8055.
for quite a while it worked mostly alright (it seemed to get initialized correctly if the usb-connector was plugged in slowly --> leaves the pic some time to get started and initialized before connected with pc, because the power contacts are longer than the data contacts. connecting it quickly, as i would do with any other device it never worked), but now it doesn’t get recognized by windows anymore, no matter what i do (all i can see is the lowest led switching on, and not switching off anymore).

this is not a mechanical fault, everything is as it should be and i have professional soldering skills (as this is my job), and it also isn’t a fault on the pc-side because it’s not been working on any of the 6 different systems i tested it on (windows xp and vista, both x32 and x64).

now one might say this is a damaged usb-connector causing all the problems, but i have thought of that before and without any result replaced the connector.

my best guess is that the pic somehow doesn’t work as it should and never has been.

the behaviour points me towards wrong fuse or initializing parameters.

i’m sorry for reporting the problem so lately, but i had a couple of very busy years.

what should i do?

thanks in advance!

luke

2

[quote]it seemed to get initialized correctly if the usb-connector was plugged in slowly[/quote] This indicates that there is something wrong with your K8055. Maybe there is a defective component on the board. See the voltage measurements etc. from the thread: [forum.vellemanprojects.eu/t/k8055-no-sign-of-life-at-all/636/1) [quote]all i can see is the lowest led switching on, and not switching off anymore[/quote] Doesn’t it give any flashes?

3

sorry, i wasn’t quite right. the led flashes twice and stays on at the third flash. will measure the voltages as soon as i’ve got some time free… (still think the problem’s something else)

4

OK. The flashes indicate that the microcontroller starts operating. The LED stays on because the PC doesn’t recognize the card as an USB device.

The only voltage check you may do is to check the voltage on pin 14 of the microcontroller. The voltage should be about 3.3V.

5

ok. i will have a look tomorrow.
is that the (can’t remember the name, pull-up voltage?) for indicating there is a new device on usb to be initialized?

6

Yes, the VUSB pin (14) is used to pull up D- line via 1.5k resistor.
According to the datasheet the VUSB voltage is 3.0 - 3.6 V.

7

ok there is 3.2V on pin 14…

8

That seems to be OK too.
This is strange problem.

9

ok. i can’t exactly tell you what the problem is or was, but it seems to be caused by one or both of the capacitors connected to the crystal. i personally hate this type of ceramic caps, because they get damaged so easily, and cause a lot of trouble… (one of the reasons i allways use smd type caps, no matter what design…^^)

anyway, thanks for your support!

luke, switzerland

10

Hello,

I’ve exactly the same problem, only on my old pc after a few retries sometimes it works ?
Do i have to replace the capacitors ?
Any help please !

11

No need to replace the capacitors if these are not visibly broken and the values are correct.
Please check once all the soldering joints before sending the unit for repair.