launchpad usb power

Even in the field, using the mini-usb port for power is a good idea.

So many nice regulated power supplies available.
Also many battery usb power packs, though test if they need minimum current draw or if they shut off.

Though it will stop working for a few seconds when you remove it to plug in the usb data cable.

The main issue is that it's a mobile robot, so they'd either need a battery pack with a USB output (weird) or to always have a laptop and move with the (very small) robot.  So the battery is the easiest (with suitable voltage regulator).

The problem we're having now is: by removing those jumpers, we lose some of the functionality of the board, specifically the pushbutton.  Since that's needed, I think we're just going to have to make sure that the students follow procedure, unless there is a way to route power to the board but not through USB?  Is there another jumper?

Mike

>battery pack with a USB output (weird)
Not weird, 100's available. just have to find one that don't shut off when current is low.

http://www.newegg.com

search for: portable battery  (or power bank) under cell phones category

Michael Stachowsky said:

The problem we're having now is: by removing those jumpers

Single jumper: VCC

Michael Stachowsky said:

we lose some of the functionality of the board, specifically the pushbutton

Pardon? Which pushbutton? Did you ever check schematics of your launchpad? - Maybe you lose power of whole msp430 - that's why you think that pushbutton does not work?

It's possible, I *am* new to this.  However, we use an external battery to power the rest of it and our booster pack works - it has LEDs on it and they are appropriately powered.  Maybe, though, that just means that Vcc is up and running.  I'm really not sure anymore, to be honest.  Does this mean that there is no way to stop power flowing from USB and still maintain all functionality of the launchpad?

Michael Stachowsky said:

Does this mean that there is no way to stop power flowing from USB and still maintain all functionality of the launchpad?

Of course it is possible to stop power flowing from USB and still maintain all functionality of the launchpad target msp430 on the LaunchPad. I wonder how you can lose pushbutton functionality if you disconnect VCC jumper. You are kindly advised to check Launchpad schematics to find all the answers you are looking for.

Michael Stachowsky said:

 I know the launchpad can be powered via usb

Exactly WHICH lanuchpad are you referring to? TI makes several different ones, and giving more information will likely help in obtaining a solution to the problem.

We are using the MSP430 launchpad.  I'm not sure which revision, but R1.3 rings a bell.  I've checked the schematics but I'm not really sure what I'm looking for.  A previous poster suggested that removing a particular jumper (J3, "VCC") would do the trick, but either it didn't work or my launchpad has a problem.

What happened when J3 was removed was that the push button failed to be detected by the 430g2553 chip.  In our particular application, the pushbutton is used to light up an LED on our daughterboard.  With J3 attached and either USB power or external power, the button lit up the LED.  Without J3 attached, the LED did not light.  I can imagine that I may have turned off power to the launchpad - since the LED is my only way to know if it's working, then either the button was disconnected or the entire system was powered off.

Mike

Michael Stachowsky said:

We are using the MSP430 launchpad.

That is still not specific. See: http://www.ti.com/ww/en/launchpad/launchpads-msp430.html#tabs

Michael Stachowsky said:

... by the 430g2553 chip.

Ok, so the MSP-EXP430G2 launchpad is what you meant.

The User's Guide is here: http://www.ti.com/lit/pdf/slau318

The schematic starts on Page 14.

When you remove the Vcc jumper at J3, you need to supply the external power in on J6. That should all work.

Yes, the MSP430G2 is correct and I agree - external power on J6 is what we use, at 3.3V.    

the strange thing is: when ONLY external power on J6 is supplied (ie: the USB is not connected) and J3 is on the board, everything works fine.  However, when external power is on J6 and J3 is removed, the buttons fail to work (or, like I said in the previous post, it's possible that nothing gets powered at all).  When both the USB and external power are connected at their appropriate locations and J3 is connected, again it all works.

I'm just concerned that the external power source and the USB power source connected together with J3 in place might damage something.  I should mention that although the ideal is 3.3V on J6, it can fluctuate between 3V and 3.9V depending on a number of factors, hence why I'm concerned.

Mike

Michael Stachowsky said:

the buttons fail to work (or, like I said in the previous post, it's possible that nothing gets powered at all

You said buttons, I said - not powered. Whatever. Actually it seems that msp430 still having power thou does not start properly. It is possible that unpowered FET does influence operation through RESET and TEST pins, so basically yes - it is good idea to remove all the jumpers to avoid any surprises.

Ah, you're right.  The other two jumpers were the issue.  I disconnected them and it works great. I suppose that with J3 removed, RST must have been pulled low?

Thanks!

Mike

Oh, and the removal of Vcc would mean that the emulator is no longer powered, and therefore I cannot use the debug option on IAR, is that correct?

Michael Stachowsky said:

RST must have been pulled low?

No. RST shall be connected to RC circuit which stays with target msp430 when you disconnect RST jumper. Again - check the schematics of Launchpad which you can find in Users Guide

Michael Stachowsky said:

Oh, and the removal of Vcc would mean that the emulator is no longer powered, and therefore I cannot use the debug option on IAR, is that correct?

No. You still can debug with disconnected VCC as long as other jumpers are in place and msp430 is powered from 3.3VDC power source

Ilmars said:

RST must have been pulled low?

No. RST shall be connected to RC circuit which stays with target msp430 when you disconnect RST jumper. Again - check the schematics of Launchpad which you can find in Users Guide

[/quote]

I'm pretty sure he meant that the unpowered FET portion of the launchpad was pulling the RST pin low (through the jumper) and holding the G2553 in reset. On the emulation side of the board the RST pin (through J3 pin jumpers) is connected to EZ_VCC by a resistor. With no voltage on EZ_VCC, the passive paths to ground will pull the RST pin down.

Yes, that's what I meant.  thanks for the info, everyone.

Mike