Using the TI Launchpad

[btcshields6]

Hello everyone.

I would like to use a TI Launchpad MSP340 as a controller for our robot this year. I've talked to a few of the more electronically minded people on my team, and I've managed to get as far as sorta understanding the circuit diagram provided by TI on this page. I've hooked it up to a battery pack and an LED to verify that it is working, and it is:



However, I'm unsure as to where to go from here. I'm only hooking up digital input buttons, but I don't know what to do next.

Our plan is to not use a ribbon cable, as we don't have an appropriate one. I can solder if necessary. I don't need to have an LED in the final project. I also don't have to use a breadboard, it was just a suggestion from our coach.

Thanks all in advance!

[ILAMtitan]

Originally Posted by btcshields6

Hello everyone.

I would like to use a TI Launchpad MSP340 as a controller for our robot this year. I've talked to a few of the more electronically minded people on my team, and I've managed to get as far as sorta understanding the circuit diagram provided by TI on this page. I've hooked it up to a battery pack and an LED to verify that it is working, and it is:

However, I'm unsure as to where to go from here. I'm only hooking up digital input buttons, but I don't know what to do next.

Our plan is to not use a ribbon cable, as we don't have an appropriate one. I can solder if necessary. I don't need to have an LED in the final project. I also don't have to use a breadboard, it was just a suggestion from our coach.

Thanks all in advance!

Glad to see your tests are working out for you. An alternative to the ribbon cables that works pretty well is using female jumper wires like these: http://www.amazon.com/40pcs-Female-2...dp/B007MRQC1K/

You can cut off one of ends, solder it to your buttons, and then plug it into the LaunchPad. It provides a secure connection that you can still modify if you need to.

I also noticed that you're in Fort Worth. If you're team is interested, FRC3005 is over in east Dallas, and we would be more than happy to host you guys after bag and tag for some OI panel building.

[btcshields6]

Thanks for the quick response and the detailed advice! We'll have to see about that after bag and tag. Sounds good though!

Thanks!

[miguelceniceros]

I was having trouble understanding the button schematic.
Using the same buttons that are used in the second example on this page, what am I supposed to connect the pins labeled "P.1" and "Launchpad MCU" to?

[Alan Anderson]

"Launchpad MCU" is not a pin label. It is a label for the device which is on the right side of the schematic, past the gray vertical line.

There are three connections on the schematic. The top one goes to +3.3V, the bottom one goes to GND, and the middle one goes to any Digital Button input.

[techhelpbb]

It appears from the schematic:

The top port is the 3.3VDC power from the TI Launchpad.
The bottom port is the digital ground reference to the TI Launchpad.
The middle port goes to the I/O pin on the TI Launchpad.

When the normally open button is depressed the 3.3VDC power is put across the resistor (current limit) and LED (light emitting diode).
With the button depressed the I/O will see a 'high' of 3.3VDC.
With the button not depressed the I/O will be pulled 'low' because the digital ground is still connected.

Assuming that's a 20mA forward current in series with a voltage drop of 1.8VDC across the LED (check the LED specifications) then R1 would be around:
3.3VDC - 1.8VDC = 1.5VDC across R1
E = I * R (Ohm's law)
1.5VDC = 0.02A * R
R = 1.5VDC / 0.02A
R1 = 75 Ohms

Alan posted before I could finish.

Normally to get that 3.3VDC regulated power for simple projects I use something like this:
LM2937-3.3

In the case of the TI Launchpad the 5V rail that powers it can come from the USB port 5V power.
It has an onboard regulator circuit that makes 3.3VDC based:
On the MSP-EXP430G2 the 3.3V regulator is the TPS77301DGKR.
On the MSP-EXP430F5529LP the 3.3V regulator is the TPS62237DRY.

That 3.3VDC is available at all the edge pins marked:
VCC on the MSP-EXP430G (TP1 on this PCB will give access to 5VDC)
3V3 pins on the MSP-EXP430F5529LP

It appears the board you have is this: (based on the image in the first post of this topic)
MSP-EXP430F5529LP

The other board (which I have laying around) is this:
MSP-EXP430G2

Sorry I revised this post a few times to capture accurate information about both 'TI Launchpads' I have seen.