MSP430 wiring when standing alone

[abioli 0]

Hi,

I made today my first test with Energia, and I got the classical blinking LED in no time.

Next, I prepared a little PCB, to wire processor in standalone (without LaunchPad): I linked a BC337, a high power LED, and whatever.

All is functioning very well until the processor stays in the LaunchPad, but when I insert it in the socket, LED is always on, not blinking.

I'm pretty sure links are ok, I give 3.3V to the source, have the ground connected, and the RST kept high with a 4.7k to source.

Is this the canonical wiring with Energia too? Or am I missing anything?

Thanks in advance for your kind help.

Andrea

[rockets4kids 204]

Do you have proper (10u + 0.1u) decoupling caps installed at the processor?

[abioli 0]

I admit that I didn't think about them, but I always wire MSP430s powering them from a very close LP2950-33, so I thought there was no need to further stabilize voltage: but you are right, I'll give it a try...

Thanks

Andrea

[Rei Vilo 695]

Also, the reset pin should be pulled-up. Reset is active low, so the MSP430 is resetting continuously.

 

Have a look at the schematics on the LaunchPad MSP430 specification sheet.

[RobG 1,892]

Can you attach schematic and/or picture? Sounds like you are doing everything right.

[rockets4kids 204]

While a MSP430 may appear to run without decoupling caps in some circumstances it is going to be prone to erratic behavior.  Not using decoupling caps is a fools errand, guaranteed to cause you much grief down the road.

[abioli 0]

Ok, it was the decoupling capacitors (or their lack, obviously...). Thanks for having pointed this out for me, @Rocket. I really thought the capacitors were something more, just 'to be sure', but now I learned the hard way that it's not true!

Thanks again to everybody, you are all very kind.

Andrea

[abioli 0]

...how can I change the topic title, adding 'Solved'?

Andrea

[Fred 453]

I'm just starting out making my own boards. I think I got most things but only allowed for one decoupling cap on the supply. Is there a "dummies' guide to your first MSP430 PCB" anywhere? Or is it worth starting one to collate your collective wisdom?

[rockets4kids 204]

http://forum.43oh.com/topic/799-using-the-launchpad-with-a-breadboard/

 

Although this is geared towards breadboard use, everything applies to PCBs as well.

 

The recommendations for decoupling caps can be found in the datasheets.  I think 10u + 0.1u is recommended for most if not all MSP430s.