CC2540: Configuring I/O reset behavior

Michael Bajema27

Part Number: CC2540

In chapter 5 of the CC2540 User guide (Doc SWRU191F), it mentions that during reset, the I/O pins are configured as inputs with pullups (P1.0 and P1.1 are inputs, but do not have a pullup or pulldown). Is there a way to change this behavior? For instance if I want to make one of the pins start as an input or output with a pulldown resistor?

over 9 years ago

0 JXS over 9 years ago

TI__Guru** 105180 points

Hello Michael,

The reset behaviour is as-described in the UG. You can configure the pins via SW after reset as described in CH 7, I/O Ports.

Best wishes

0 Michael Bajema27 over 9 years ago in reply to JXS

Prodigy 100 points

But can you change the behavior in low power mode? I know I change the behavior after reset. My issue is when it is in low power mode, all the pins are at VCC and they're turning on stuff I don't want on until after the uP has finished starting up.

0 YiKai Chen over 9 years ago in reply to Michael Bajema27

Guru 735695 points

You can add GPIO settings inside halSleep() (in hal_sleep.c) then the GPIO would be set before it goes to sleep mode.

0 Michael Bajema27 over 9 years ago in reply to YiKai Chen

Prodigy 100 points

Ok I need to be more specific. My device does not have power. When I give it power, all the I/O are pulled to VCC for the time it takes for it to get to 3.3V. During that time, anything I want at logic low, is at VCC and that is a problem. Can I keep them from being pulled to VCC when the power is below the minimum turn on voltage?

0 YiKai Chen over 9 years ago in reply to Michael Bajema27

Guru 735695 points

You cannot change the startup default status of IO pins. You can only change it after application gets CPU control.

0 Fredrik K over 9 years ago in reply to YiKai Chen

TI__Guru** 106705 points

As you write in your original post, P1.0 and P1.1 do not have internal pull. On these pins you can thus safely add external pull-downs and the pins will stay low during Reset.

Regards,
Fredrik

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CC2540: Configuring I/O reset behavior