UNO With RS232 - Power RS232 From Digital Pins

I am running 12 - DS18B20 1-wire temp probes with the arduino. I want to send the temperatures to a Creston PRO2 processor thru a RS232 shield, mounted on my arduino. My problem is that a program can’t be uploaded to the arduino with the RS232 installed. With a little experimenting I found I could install a switch between the 5v power output pin on the arduino and the power input on the RS232 while the RS232 is mounted. It seems to work vary reliably, at least for sending data out thru the RS232 line.

My question is can I power the RS232 using the digital output pins on the arduino.(Enough power) I can run 2 or more pins in parallel to increase power if need be.

If I can do this and I think I can, is there any way a running program can tell when a program is starting to be uploaded and turn those pins off, so I can successfully upload the new program?

Well, you should read the shield datasheet and see which is the power requeriment. I doubt a digital pin can give enough power, but you can use a transistor attached to a digital pin to power the shield connected to 5 volts.

Are you wondering if you can power your shield from digital I/O pins rather than from the 5v pin because you can switch the I/O pins off under program control?

I think the safest answer is NO.

Why not put a transistor between the 5v pin and the Shield and use an I/O pin to switch the transistor on or off?

If you can use a Leonardo or a Mega with extra serial ports you could probably just interface to the RS232 with a Max232 chip and not need any shield.