sleep mode for PIC

[Rajinder]

Hi
I am using a PIC 18F4550 and want to put it into sleep mode to conserve battery life then wake it up using a 'wake up from interrupt'
My question is what I need to do with the I/O lines?
A basic sleep function will put the PIC into a mode which it consumes around 40uA.
However, if other things such as I/O lines, WDT etc are configured correctly, the current consumption can be reduced further.
Any help would be appreciated.
Thanks

 

[kellys_eye]

The datasheet should specify the various requirements and/or configurations for sleep mode.

What does the manufacturer say?

 

[HellasTechn]

I was just about to suggest a datasheet also such info would only be found in there !

 

[Sadlercomfort]

Is your question how to put the microcontroller into sleep mode? Or specifically how to setup the config bits and I/O lines to reduce power consumption?

 

[Rajinder]

It is how to set the configuration bits and I/O bits to reduce the current consumption further.

 

[Sadlercomfort]

I think the simplest solution is to disable all the config bits and there functions.. Since the watchdog timer, timer1 etc will consume power.

If you post your circuit diagram we may be able to simplify it to consume less power. Also, this document is very useful: http://ww1.microchip.com/downloads/en/DeviceDoc/01146B_chapter 2.pdf

 

[Rajinder]

Hi,
Thanks all for your replies.
If I make the I/O ports as outputs and drive them low, turn off A/D, UART etc
Would that be enough?
Raj

 

[BobK]

Depends on what is connected to the ports. For example, if there is an LED beteen V+ and the port, you would set it to high to minimize current,

Bob

 

[Rajinder]

The program flashes an led on for 1 sec then off for 1 second. The port line driving the led is then made high. Note the led is driven by a pull up to 3v, cathode to pic I,/o line.
The other ports have nothing connected, so I made them all o,/p and driven them low.
The pic uses the internal oscillator.
However using the following inline assembler code after the led is off:

asm sleep;

Results in 4-5mA still being drawn by the circuit. I think it should be around 5uA.

Any ideas?