11/3/2014 square-disk: Beyond The Development Board

http://square-disk.blogspot.com/2010/08/beyond-development-board.html 1/4

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Saturday, 14 August 2010

Beyond The Development BoardI was just asked a great question in response to my YouTube clip of the Time Lorddemo: "Will the programmed micro work without the launchpad kit?". I was just going write aquick 'yes' in return since my next project revolves around that ability.

Yet as I hovered over the 'Post' button I realised this was merely an assumption; I had nevertested it for myself. So I pulled out some jumper wires and quickly connected the Time Lordchip to a single LED and a battery pack as a quick proof of concept.

I was briefly stumped when the LED remained dark. I double checked all the connections butfound no shorts or faults. Using a voltmeter I probed the LaunchPad board's DIP socket andquickly discovered my problem, the RST pin on the LaunchPad was being supplied withcurrent!

I did some Googling and confirmed the microcontroller is held in the reset state while theRST pin is low. After adding a wire between RST and the postive battery terminal the LEDcame to life as expected.

The final jumper wire connections were as follows:

Red - Positive battery terminal to MSP pin 1 White - MSP pin 2 to LED anode Green - LED cathode to negative battery terminal Yellow - Positive battery terminal to MSP pin 10 Black - MSP pin 14 to negative battery terminal

_glytch

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11/3/2014 square-disk: Beyond The Development Board

http://square-disk.blogspot.com/2010/08/beyond-development-board.html 2/4

Posted by _glytch at 17:44

Recommend this on Google

8 comments:

Tabish Chasmawala 16 August 2010 12:03

Pretty Cool... Why not breadboard the microcontroller and connect with twopushbuttons and LED just like your Time Lord game?

Reply

NJC 16 August 2010 13:18

Sorry for all the comments :-P

Gareth, it would be a good idea to hook up the RST pin with a resistor to the positivebattery terminal. There are multiple reasons for this, but I won't go into it here. It isalso a good idea to use a low value resistor in series with the LED to limit thecurrent draw.

I'm jealous of all your cables :-P very cool.

Reply

Gareth Williams 16 August 2010 15:40

Tabish,Sadly I don't have a breadboard yet otherwise I would have (I only got around toordering one last week).

NJC,Do you know what the minimum voltage would be to keep the RST pin happy? I don'trecall seeing it in the datasheet but I am new to reading them. I am now using a150R inline with LEDs to limit them to 20mA on a 3v supply and all is good.

All tips are greatly appreciated, everybody!

Reply

Tabish Chasmawala 18 August 2010 15:57

So what is your next project Gareth?

Reply

Gareth Williams 18 August 2010 22:19

I'll have a post up tomorrow about it, Tabish :o)

It's going to be a multi-post project on account of the fact I suck at circuit boardlayout - I just built my first ever board yesterday! It's fairly small and basic but stilltook me most of the day :o(

I planning a sort of enclosure too. Hopefully it'll be a bit of a progression from thejumble of wires in the video above.

Reply

bluehash 19 August 2010 03:48

11/3/2014 square-disk: Beyond The Development Board

http://square-disk.blogspot.com/2010/08/beyond-development-board.html 3/4

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Nice hack. I'll blog about this in a few minutes. You could even use a coin cell topower it up. Make an LED throwie!

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Anonymous 24 September 2011 09:34

Hello. If u do get this comment, make sure in the future, to connect the reset pinHIGH by a pull up resistor (47K ohm) connected directly to the V+ of the powersupply and make sure that the Vcc pin is decoupled by a 0.1uF capacitor---> helpsto give a clean AC free DC voltage to the uC

http://dangerousprototypes.com/docs/MSP430_quick_start

This might help!!!. Happy coding

Reply

_glytch 24 September 2011 16:12

Thanks for the tips, Anon.

I've never found an explanation for the pull-up resistor on the reset pin. The circuithas been working perfectly for ages without it. I guess it is just to reduce power drainthrough this pin?

Also while the cap would be pretty crucial for a circuit powered by an AC-DCconverter surely a simply battery will provide a clean enough supply that this filter isnot required?

I'd be interested to read your thoughts.

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