18F2455, USB-HID, random error, help me please

denkid · Joined: 17 Jan 2005 Posts: 10

Hello.

first, thank you for reading my question.

second, my english might be very poor, sorry.

* PROBLEM

I made ten PIC(s) it can connect to PC with USB-HID

The PIC(s) is consisted of 20Mhz External OSC

and It running 48Mhz MicroProcessor Mode

I said I made 10 PIC(s)

but, just 5-6 PIC(s) is working.

remain (5-4) PIC(s) is not working.

* THE RANDOMLY ERROR

at the first time connected to USB

it seems to be right. but 1~2 minutes after.

i can hear the sound "USB DISCONNECTED SOUND"

(as you know, USB Sounds are CONNECT, DISCONNECT, ERROR, etc...)

and then, when I connect again that is disconnected PIC.

I can not hear the sound "USB CONNECTED"

so It is not working anymore....

* TALKING

I made over the 100 PIC(s) up to now,...

I wasted about 40 PIC(s).

and, I am afraid remained 60 PIC(s) it will be changed to "RANDOMLY ERROR".

Please help me.

0. I did not use "SHEILD LINE" in USB cable
1. I Blocked Electrical Shock using Ground
2. I use Elnec "SMART PROG Perallal Port"
3. I use 1.5K resister on USB Data Line
4. I use 4.7uF capacitor on Vusb
5. MCLR is made as recomanded.
6. USB Voltage Regulator is Enabled (PIC is a little hot)

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

You should look at the Microchip USB forum. Here's the link:
http://forum.microchip.com/tt.aspx?forumid=102

Also use the Search page on the Microchip forum.
http://forum.microchip.com/search.aspx

Here are some posts that I found by using the search page to search
the USB forum, and search for: disconnects
Look at all these posts. See how the Microchip USB forum is much
better in terms of answering Microchip USB questions.
http://forum.microchip.com/tm.aspx?m=236558&mpage=1&key=disconnects&#236558

Here's somebody else with your problem. No answers.
http://forum.microchip.com/tm.aspx?m=152035&mpage=1&key=disconnects&#152035

This one may have an answer for you:
http://forum.microchip.com/tm.aspx?m=119076&mpage=1&key=disconnects&#119076

http://forum.microchip.com/tm.aspx?m=181612&mpage=1&key=disconnects&#181612

http://forum.microchip.com/tm.aspx?m=248476&mpage=1&key=disconnects&#248476

denkid · Joined: 17 Jan 2005 Posts: 10

I am reading informations

thankyou

and I am waitting for anyother comment you have.

Thank you so much

denkid · Joined: 17 Jan 2005 Posts: 10

I tested other OSC configuration using broken PIC (Disconnected USB)

for example, internal osc.

it is still working. (of course, external osc is not working)

but, internal osc can not support USB.

I think (It might be wrong..)

1. Internal OSC circuits of PIC is broken.
2. Internal USB Regulator is broken.

Thankyou for reading

Ttelmah · Guest

Why have you got a 1.5K resistor on the USB data line?.
The PIC has internal resistors. Have you disabled these?.

Are you using the USB connection sense circuit (two resistors from the USB power to a pin on the PIC). If so, have you enabled fast_io on the port with this connection - if you don't, and output a value on this port, you can hang the USB.

I see no mention of supply smoothing for the PIC itself.

What else is the PIC driving?. The chip should _not_ run hot. Even with the USB regulator enabled, the total power dissipation of the chip is tiny, unless you are driving something else.

Put a smaller capacitor on Vusb. The problem is that 4.7uF, almost certainly implies an electrolytic capacitor. These can have poor HF performance. The capacitor on this line provides two functions. A degree of 'reservoir', and stabilising the regulator from oscillating. An electrolyic capacitor, may not perform this second function, leaving the regulator oscillating. If this happens, it will run hot, and may well fail.

Best Wishes