Hi, As mentioned, I am trying to use the SR04M-2 to measure water level. I am trying to keep the Arduino (nan0) board about 50 feet away. Hence, use Automatic Serial port mode So as the calculation is done in the module (and not by the microcontroller). Also, to keep the baud rate small (300 bauds?) due to the distance. Can you please provide some pointers to change / set the baud rate? And/or any other pointers for this requirement? Wholehearted thanks.
Hello tsrajesh
Welcome to the best Arduino forum ever 
Post a block diagram with all the components used.
A picture is always worth a thousand words.
What makes you think that the baud rate can be changed?
I have seen no mention of changing it in any of the documentation that I have seen.
As far as I know It is fixed at 9600 Bd.
There is a tutorial here, about changing modes by selecting various resistor values for R27. All 3 modes using serial communication are 9600Bd.
Thanks for responding.
I got several pages that describes changing the mode.. but I can't find any full fledged datasheet. It is just my assumption that the baud rate wouldn't have been hard fixed.. and Only the bare minimum to get it to work is published. I'll have to think of some way to cover the distance.. Wired or wireless.. Which could even mean having two microcontrollers instead of one...
You could use a UART to RS232 converter, or UART to RS485 converter at each end.