Hello Minh Nguyen, hope you are doing great,
Often times the USB bus in front of the computer has a splitted power supply meaning that the maximum power output for each of the USB ports in the front is splitted. In case you have a 500mA USB Bus the ports in the front we will have 250mA at maximum each, this been said often times you are not going to be able to power to different devices from the front ports.
This does not happen very often with the back USB ports of the computers so my first recomendation would be to use a different set of USB ports, plug the devices in the back of the computer instead of the front.
Seems like either of the USB devices you have needs close to te maximunm power supply that the BUS can provide.
A good option also is to have a powered USB hub to supply enough power to all your USB devices.
Regards,
Luis A.
Applications Engineer.
National Instruments.
