Mosaic
Well-Known Member
Hi ,
I am running a 16F886 @ 5v and I want to place a pair of 1.5V dry cells as a 3V battery backup with a low Vf schottky blocker. I don't have any pins free, but I was wondering if I place a 39K resistor inline with the primary supply (12V DC) to the TX RS232 pin and use that pin as a digital input to sample the voltage if that would be a reasonable way to monitor the main supply. The built in PIC clamping diodes could handle the 0.3mA overvoltage load.
I need the PIC to detect the loss of main supply and enter a current saving mode to just maintain a clock.
When RS232 ops are called for I can momentarily stop the voltage monitoring to execute comms.
Would that 0.3mA pull up affect RS232 comms?
I am running a 16F886 @ 5v and I want to place a pair of 1.5V dry cells as a 3V battery backup with a low Vf schottky blocker. I don't have any pins free, but I was wondering if I place a 39K resistor inline with the primary supply (12V DC) to the TX RS232 pin and use that pin as a digital input to sample the voltage if that would be a reasonable way to monitor the main supply. The built in PIC clamping diodes could handle the 0.3mA overvoltage load.
I need the PIC to detect the loss of main supply and enter a current saving mode to just maintain a clock.
When RS232 ops are called for I can momentarily stop the voltage monitoring to execute comms.
Would that 0.3mA pull up affect RS232 comms?