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FT232RQ reset problem - works fine after heating up the device.

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LeNiCiDE:
Hi

I've got strange behavior of my PCB. When I take the device and plug it in for the first time Windows can't recognize my board. If I reset the FT232 on RESET pin everything is ok. When I heat up the device with hot air the problem dissappears - FT232 is recognized by PC. What can cause that, I've tried various combinations I've even desoldered ADUM5020 and ADUM4160 from the board.

If the device is connected and I take out the cable, next connection can be established - sometimes it isn't. But when I move cable a little bit to disconnect only data pins (not power pin) device is recognized by PC (this trick with not fully disconnect cable works only if the device established connection with windows before cable movement).

Here is scope image of the reset pin after plugging in the cable - no connection established (blue RESET, yellow VCC on VCC pin of FT232):
"low_temp.png" (see attachment)
Here is scope image of reset pin after heat up with hot air and plugging the cable (connection established):
"high_temp.png" (see attachment)

Power seems OK.

FTDI Community:
Hello,

You are already in contact with our technical support team on this matter via email.

Please feel free to post any resolution here to help other community users.

There may also be other FTDI Community users who will be able to help you.

Best Regards,
FTDI Community

LeNiCiDE:
Thanks to FTDI support - the issue was with floating TEST pin. Pin was floating - this is the cause of problem. Heating up the device was successful solution because of this floating pin.
Read the datasheet carefully! (see attachment). Connecting this pin to GND solved the issue.

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