Power for the TI LaunchPad
September 28, 2010
Power for the TI LaunchPad can be supplied via the USB connector. The USB power is +5V. Apparently the onboard FTDI chip converts the 5V to 3.3V for the MSP430 microprocessor. The micro power is 1.8 to 3.6V.
I'm planning a home-made shield for the LaunchPad, and I will need more than just the 3.3V for motors, servos, sensors, etc. The 3.3V from the FTDI is very current limited anyway.
So a 5V Low Drop Out (LDO) regulator will be included. When I'm running off batteries, I will also need a 3.3V source for the micro. I considered a 2nd 3.3V voltage regulator, but then I found this article on Connecting a Parallax PIR Sensor module to the LaunchPad, by suspended-chord.
He pointed out that the LaunchPad has several tie points, including TP1 and TP3. They are located need the USB connector. He writes:
"TP1 is connected to VBUS (USB's Voltage, which happens to be 5V), and TP3 is connected to the USB's GND."
So I'm going to try populating my shield with just a 5V regulator, and running the 5V from that to TP1/TP3. I just have to be careful to switch off my battery power before connecting the board to USB, so I don't have two sources trying to run to the board.
I don't know if this will work, and I hope I'm not going to damage the board somehow. If everything goes smoothly, I'll have Vin (battery power) and regulated 5V available on the shield, and 3.3V for the micro and anything that needs it.