Well from the commands you use in the VI I actually doubt that your mbed pump controller is using the RPC_Serial_LPC1768.bin firmware that your LabVIEW RPC VI library is supposed to connect to. Instead it may implement its own firmware that is specific to the pump control logic.
And if the RPC is indeed the solution you are looking at (does the Matlab code also use the same RPC_Serial_LPC1768.bin frimware file?) then you most likely should not create two RPC objects from one serial port, but instead branch the class wire after the SerialRPC.vi. Otherwise you end up getting an error in whatever SerialRPC.vi executes as second, since the port is already in use.
the .bin file you mentioned is already in the mbed driver and it's the same used for Matlab. I tried to branch instead of having another RPC serial but changes nothing, I connected the 2 cables which were supposed to be on mbed pins 11, 26 with a frequency generator and the pump runs as needed. I'm really confused I mean everything seems to me as correct, could it be that I need to write another .bin for the mbed for this program I wrote, like sending pwm and other stuff or what? do you have any other ideas?