|Now we see why TI calls it the 'Launchpad'. You program the MSP430, then launch it off to it's destination. Notice the empty socket on the Launchpad in the foreground, and the MSP430 microprocessor ruling the breadboard in the background. Fun stuff!|
I got my feet wet with my first Arduino circuit the other day, now it's time to get started with the TI Launchpad's 'Hello World' circuit. The MSP-430 chip is preloaded with the code, so I decided to try something new and build the circuit on the breadboard, without the Launchpad board at all.
It's a very ugly circuit, mostly because I decided to put two AA batteries on the bread board too. I wired them up in series, supplying the MPS-430 with 3.2 volts. The only battery pack I have wired up is a 9V battery pack, and I didn't have a voltage regulator on hand. I could have hacked up a USB cable, but that would still leave me at 5V, well over the max input voltage of 3.3V. So I was stuck with either using a AA battery or two or plugging USB into the chipless Launchpad board, then taking the 3.3 volts out of the regulator and jumping it over to the breadboard. I wanted to do it all on one board though.
Sidenote - when fooling with the Launchpad board earlier I was using a 9V battery as the input, assuming the onboard voltage regulator would knock the voltage down to the required level. I was curious about the tiny voltage regulator, so I found the part number in the manual - TPS77301DGKR ( .87 at Digikey). The part shows an input range of 2.7V - 10V, but it has a variable output range also of 1.5V-5.5V. I tested the Vcc-in and found 5.4 volts - way too hot. So, the bottom line is you want to keep the input voltage at 5V or less to get 3.3 V at Vcc. Nowhere in the manual does it tell you this, I had to figure it out looking up the part info and testing with the multi-meter.
So, I decided to build the Hello World circuit on the breadboard to showcase one of the features the Launchpad has over the Arduino Uno. Not only can you program the MSP-430 chip in place, but you can simply pull the programmed chip out of the socket and plug it into your breadboard and you're ready to go. The Arduino Uno's Atmel chip, at least on my version, is an SMD part that is soldered to the board, so it's really only useful for prototyping only. Not only can the Launchpad program and 'launch' the finished MSP-430 to the destination board, but TI was thoughtful enough to include another MSP-430 chip in the $4.30 development package. There is a MSP430G2553 in the Launchpad socket and a spare MSP430G2452 in an anti-static bag in the box.
The build was pretty simple, as ugly as it looks. I had to get creative in a few spots because of all the room the AA's were taking. The only part I struggled with was the reset pin. I had read at http://www.43oh.com that someone had forgot to hook up the reset pin. So I was on top of that, I thought. I kept hooking the Reset pin up to ground, trying different amounts of resistance, etc., but nothing worked. While I was doing that, I figured out that I had fogotten to hook up the ground lead of the micro. DOH! Then it took me another 30 minutes to give up and look at the post at 43oh that I had read earlier. The reset pin goes to Vcc not ground dummy! Double DOH!!! I hook the Reset pin up to Vcc and the circuit works like a charm. Success!
Another side note - I decided to try the AA between the headers trick after reading the Instructable.com - Guerilla Battery Holder for your Breadboard. The only difference is they were using a coin sized 3V cell. I can attest the trick doesn't work near as well with a AA. But it worked.
This Hello World project was VERY satisfying. A very simple circuit but I learned a ton, and once I realized how easily I can throw a $1 microcontroller on a breadboard and make it work...I start to realize the possibilities. At least for this first project, the TI Launchpad showed a lot more versatility and value than the Arduino Uno...especially at the price.