How can we change pin assignments ?

LazBoy · Joined: 17 Oct 2006 Posts: 8

Dear friends,

How can we change pin assignments for same process routines
at runtime ?

Not for DS1820 specific problem, just an example:

jma_1 · Joined: 08 Feb 2005 Posts: 147 Location: Wisconsin

Greetings,

I do not like using global flags, but if you know which function you are calling, set a flag and use the flag to signal what inputs you want to measure. Check the flag inside your routine for which pins to measure (maintains your calling routine).

something like

if (m_bFlag)
{
data = read_adc(my_pin1);
}
else
{
data = read_adc(my_pin2);
}

I'm not sure I understand your problem. Do you have one 'read' function or two? If two you do not have a problem, just use the pin internal to that function. If not, the 'flag' idea might be acceptable. Or make two read functions and call the appropriate one Read_ds_indoor(), Read_ds_outdoor(); Or create a function which scans all your pins continusously one each iteration of your main().

Cheers,
JMA

LazBoy · Joined: 17 Oct 2006 Posts: 8

Thanks for reply jma_1,

#define LED PIN_A2

As a summary:
Can we change this definition at runtime ? Possible ?
Or there are any methodes for this ?

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

LazBoy · Joined: 17 Oct 2006 Posts: 8

Thank you.

C Turner · Joined: 10 Nov 2003 Posts: 40 Location: Utah

The best way to do this would be to use the same pin for both temperature sensors - but this does, admittedly, complicate things very slightly.

First, you would connect just the "outdoor" sensor, then read its serial number from ROM (using the "READ ROM" command) and then store it in the PIC's EEPROM.

You would then disconnect the "outdoor" sensor and connect the "indoor" sensor only, read its serial number from ROM and then store that in the PIC's EEPROM.

In doing this, you'd have the serial number from both devices and would then be able to put both on the same I/O line and address them independantly using the MATCH ROM command and this would require only one line.

Of course, if you use parasite power, you'd be able to only do one conversion at a time as you'd have to wait for one to complete and then read it before stating conversion on the the other unit.

Alternatively, one could use the "serial number discovery" process to have the PIC determine what the serial number of each unit was on its own - but you'd still have to figure out a way to tell it which was the indoor and which was the outdoor.

CT