LPC1114/301 PIO0_1 pull down problem & failure problem

[lpcware]

Content originally posted in LPCWare by jschimpf255 on Wed Feb 25 17:43:23 MST 2015
Hi,
  I have a built a board as a RS-232 <-> I2C interface for a sensor.  The LPC1114 has RESET pulled high(15K resistor)  (serial RTS can pull it low) PIO0_1 pulled high with a 15K resistor but with a jumper to pull it low for programming.  The serial lines are connected to a RS-232 interface chip and the I2C lines connected to the sensor. None of the other lines except power and ground were connected on the LPC1114.

  A number of the boards were successfully programmed with FlashMagic and were working initially.  The next day trying the boards none of them worked.  (they were kept in antistatic bags and handled carefully) Examining them the PIO0_1 line is pulled low, even with the ground jumper removed.  If I pull RESET low PIO0_1 reverts to an input and goes high till reset is released.  Also the failed boards seem to draw more current ~ 10 ma where before it didn't register on the power supply meter.

  The chips have not been reprogrammed, at this point they won't connect to FlashMagic.  I am trying to find out what I have done wrong.  I would like to re-spin the boards to correct my mistake but I have to find it. 

  This design was prototyped using the DIP-28 version of the LPC1114 (and with the same version of the Analog Devices RS-232 chip) and none of these problems happened.  This prototype was treated not too gently (handling and static wise) and still works fine.

Thanks very much for any suggestions.
--jim

[lpcware]

Content originally posted in LPCWare by R2D2 on Fri Feb 27 18:05:06 MST 2015

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Quote: jschimpf255
Examining them the PIO0_1 line is pulled low, even with the ground jumper removed.

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:~

Did you disconnect RS232 interface?

Did you scope Reset and ISP pin?

[lpcware]

Content originally posted in LPCWare by jschimpf255 on Fri Feb 27 17:13:02 MST 2015
I changed the code to set it to an input and that didn't help.  Also boards that had worked one day stopped working the next day.  No change in code (i.e. they weren't reprogrammed).  I am trying to see what I might have done wrong on the board design.  I realize that is something rather difficult for you to diagnose. But is leaving all unused lines floating safe ?  Thanks for the help.

--jim

[lpcware]

Content originally posted in LPCWare by xianghuiwang on Fri Feb 27 16:17:36 MST 2015
hi,
It seems your code is making PIO0_1 an output. We suggest you run your exact code on your prototype board and confirm the execution.
regards!