Bootloader vs UART port

[Oznog]

I was looking at using the UART module inside the PIC18F452 to talk to a Garmin GPS through the NMEA-0183 protocol. Typical config is "4800 baud, 8N1 (eight data bits, no parity, 1 stop bit) with no flow control". It uses only 0-5v TTL levels.

I wanted this same system to also use a bootloader. The board is wired through a MAX232 chip but I haven't actually tried to make it work yet.

But I see that the PIC's UART used RC6-RC7 pins, or looking at some GPS projects people just went with the Rx pin. Now I have two questions:
1. Will the GPS being plugged into the RC6 pin at powerup be able to erroneously begin the bootloading procedure, thus ruining the code space?
2. Will the MAX232 chip be able to read 0-5V TTL levels too, so I could plug the cable from the GPS into the same DB-9 plug used for bootloading?

 

[evandude]

typically bootloaders would only begin their sequence when specific "handshaking" commands are sent between it and another device. The one I use, you set the program on the computer to program, and it waits for the pic to send a certain character (which it does on boot) and then responds and begins the process... unless your GPS unit sent exactly the right commands at exactly the right time you should have nothing to worry about

 

[TKS]

if it still does think about a transistor construction using one port of the pic wich will put the gps unit on soow if the pic is in bootloader **** the gps is off...when program start the gps is powered up..maybe a delay is needed in the pic..


TKS