DIO internal PullDown

[neil]

Hi Mark,
  Hope you are doing well..

Its been quite a while since i have done anything on the MFC52259, and dont have anymore much info on programming it. I am wondering if utasker has something I can use   for setting PortA for input and assigning internal pulldown.  Im using the Port A , pin 5 as input as follows:

DDRAN &= ~PORT_AN_BIT5;   //se

if(PORTIN_SETAN & GSM_PWCTRL_PIN)
 ...

But it must be using internal pullups , I really want internal pulldown. Can t add resistor as the units are already in the field.

Many thanks
Neil

[mark]

Hi Neil

Unfortunately AN doesn't have any internal pull-up or pull-down capabilities - see attached image.

Regards

Mark

[neil]

Hi Mark,
  Many thanks for that information. 

Strange though, as when nothing is connected to PA5 (same with a couple of other pins) , it is sitting at 3.3v. 

Best Regards
Neil

[mark]

Hi Neil

I wonder what happens f you connect a 1MOhm resistor to GND from the pin?
If it then goes to '0' it would presumably mean that there is a very low leakage path to 3V but not enough to supply any real current.

Regards

Mark

[neil]

Hi Mark,
  I will give that a try. I am using to to read a pin from a modem, the modem keeps this high, then drops to 0 when switched off. But I cant monitor it as always sitting high. I have many units out there now , and would have put a pull down resistor on it but cant get to them. I will just have to use a timeout of these.

Many thanks for your help

Best Regards
Neil