sketch upload speed

I built a programmable power supply using a Atmega328 (no P) and I monitor and graph the voltage and current by connecting it to my PC via a Sparkfun FTDI USB breakout. I also reprogram the unit using the latest Arduino IDE and the same interface. It was working great but then I wanted to isolate the USB ground from the microcontoller ground so I inserted an optocoupler. Now I can still monitor/graph the power supply but I can't upload new sketches. I suspect it has to do with the baudrates. I monitor/graph at 19200 because that's about the limit of my optocoupler design. I'm using the Arduino bootloader. Can someone explain to me where the two ends of the sketch upload baudrate are set? I see the upload speed in boards.txt is 56700 so I figured that was one end of the connection but I'm confused about the other end (chip side).

EnzoMango: I built a programmable power supply using a Atmega328 (no P) and I monitor and graph the voltage and current by connecting it to my PC via a Sparkfun FTDI USB breakout. I also reprogram the unit using the latest Arduino IDE and the same interface. It was working great but then I wanted to isolate the USB ground from the microcontoller ground so I inserted an optocoupler. Now I can still monitor/graph the power supply but I can't upload new sketches. I suspect it has to do with the baudrates. I monitor/graph at 19200 because that's about the limit of my optocoupler design. I'm using the Arduino bootloader. Can someone explain to me where the two ends of the sketch upload baudrate are set? I see the upload speed in boards.txt is 56700 so I figured that was one end of the connection but I'm confused about the other end (chip side).

For sketch uploading operation the baudrate in the boards.txt is what the Arduino IDE uses to set the PC side of the link. The 'other' side is 'hardcoded' into the bootloader code so cannot be easily changed by the user without recompiling and burning a new bootloader into the mega chip and creating or selecting a compatable boards.txt entry.

Lefty

thank you Lefty! Since it sounds difficult to change the baudrate and the power supply won't be connected to a load when I upload a new sketch, I'll take the easy way out and bypass the coupler during sketch uploads. I figured it might be more complicated than it was worth, but I wanted to make the decision based on knowledge rather than ignorance...