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Raj Nambiar
03/31/12 08:42
Read: 4327 times

#186952 - FTDI F232RL Noise issues
Using FTDI F232RL for USB to serial interface at the output of a UPS. Chip keeps freezing when connected to PC application. It works again after it is taken taken out. Application is written by us, and we can see that the chip is hanging at that point. If I use another PC to emulate the UPS, then it works fine. Even when I test it between two PCs to transfer info, it works fine even if keep connecting and disconnecting the serial port side every second. It works in a very stable way if I remove the USB and put it back many times.

We can connect the UPS output to other devices that accept serial port data - remote display / SNMP agent hardware etc. All of them run fine. UPS is ours. We don't find any noticeable spikes at the serial port side. Serial port of the UPS, is also opto isolated from the other part.

Problem happens only when the card serial port side (just a small pcb , with f232 and max232 as per their pdfs) is connected to sme other serial port. If I make a test device with a pic controller + max232 serial port powered from a linear regulator sourcing power from a 9v transformer + rectifier, and use that device to drive my serial to USB, freeze-up happens ie: f232r hangs if I keep connecting and removing the ground pin of serial port. Else, it is stable.

FTDI guy says the problem is with noise. We have done more than what they recommended in their documents. Proper decoupling, ferrite beads even in Rx/Tx/Line of serial port etc. Tried bigger caps at the power supply source side of PCB (USB bus powered) - even tantalum ones. Error handling is done in PC app, including pipe reset count, timeouts etc.

I have seen some posts talking about F232R freezeup when relay is activated/ motor is running etc.But these posts were not with useful resolutions.

Any suggestions to deal with the freeze-up? FTDI guys are not being helpful.

Regards, Raj

List of 36 messages in thread
FTDI F232RL Noise issues      Raj Nambiar      03/31/12 08:42      
   GND,cables      Stefan KAnev      03/31/12 11:51      
      of this is it, then      Erik Malund      03/31/12 14:19      
   leakage effects..      Jim Granville      03/31/12 16:46      
      Thanks for the comments..      Raj Nambiar      04/01/12 02:02      
         changing the serial port data....      Stefan KAnev      04/01/12 05:11      
         cable, bought off the shelf      Andy Neil      04/01/12 09:00      
            Test standard solutions      Jim Granville      04/01/12 14:54      
               Options..      Raj Nambiar      04/01/12 23:44      
                  VCP /D2X      Stefan KAnev      04/02/12 03:37      
                     Problem exists with both drivers      Raj Nambiar      04/02/12 08:34      
                  Aten serial to USB cable uses a FTDI chip      Kalpak Dabir      04/02/12 04:16      
   FTDI chip ESD sensitivity        Oliver Sedlacek      04/02/12 06:13      
      Thanks Oliver...      Raj Nambiar      04/02/12 08:30      
         Zeners are slow      Erik Malund      04/02/12 08:59      
         show Your circuit      Stefan KAnev      04/02/12 11:04      
            F232 is USB powered but.. + circuit      Raj Nambiar      04/03/12 01:32      
         USB Isolator Chips      Neil Kurzman      04/02/12 21:50      
            Isolators      Raj Nambiar      04/03/12 02:00      
         Better than zeners      Oliver Sedlacek      04/03/12 07:30      
            just a thought      Erik Malund      04/03/12 07:45      
               Layout      Raj Nambiar      04/03/12 22:13      
                  VCP/Direct drivers      Raj Nambiar      04/03/12 23:49      
                  Layout attached      Raj Nambiar      04/04/12 00:51      
                     It's a high speed circuit !!!!      Oliver Sedlacek      04/04/12 05:09      
                        Totally 100% Agreed      Michael Karas      04/04/12 05:34      
                           the trouble with schematics ....      Erik Malund      04/04/12 07:36      
                              Bandwidth limitation      Per Westermark      04/04/12 09:08      
   22 ohms between serial port ground and FT232 ground helps...      Raj Nambiar      04/05/12 23:58      
      of course it does      Erik Malund      04/06/12 08:01      
         Erik,      Raj Nambiar      04/06/12 09:45      
            Links please      Bert Van Den Berg      04/13/12 13:44      
               Link...      Raj Nambiar      04/16/12 00:12      
                  Solved      Raj Nambiar      06/15/12 23:59      
                     Magnetics      Per Westermark      06/16/12 02:08      
                        Ethernet input is connected to serial port ground      Raj Nambiar      06/22/12 08:56      

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