ISP GPIO state

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ISP GPIO state

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lpcware
NXP Employee
NXP Employee
Content originally posted in LPCWare by lenguyen on Mon May 19 14:43:55 MST 2014
Hi All,

We are about kickoff first phase of PCB and software design and move on second phase of our design and development. We had learned and fixed a number of issues/problem in our design, LCPOpen, LPCExpresso and Debugger. However there is a big question that we need resolve before we can feel much comfortable. We have been seem the number of MCU jump into ISP at the power up cycle. I understand we need to do in our side to fix this problem however our system includes heating control, stepper control and so on. To be safe we need make sure all of this module to be off if MCU is in ISP mode. Our question is when MCU is in ISP mode, what're all GPIO state ? There is any specific GPIO known state that we can use to turn off our heating module ?

Thank you
LN
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lpcware
NXP Employee
NXP Employee
Content originally posted in LPCWare by lenguyen on Tue May 20 11:50:00 MST 2014
Thank you.
L.N
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lpcware
NXP Employee
NXP Employee
Content originally posted in LPCWare by R2D2 on Mon May 19 14:58:58 MST 2014

Quote: lenguyen
Our question is when MCU is in ISP mode, what're all GPIO state ? There is any specific GPIO known state that we can use to turn off our heating module ?



Your ISP problem is usually a pull-up problem (ISP pin pull-up and Reset pin pull-up)...

ISP GPIO state is default = usually input / pull-up.

To avoid problems you should switch low active or add a pull-down...   


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