Set of noob questions !

[vadimVladimir 0]

Hi all, I just started with msp430. I am very noob !!!

 

First question: How do I set the Status Register bits in C?

 

slau144j.pdf assembly example, setting CPUOFF and GIE bit:

; Enter LPM0 Example

BIS #GIE+CPUOFF,SR ; Enter LPM0

 

; Exit LPM0 Interrupt Service Routine

BIC #CPUOFF,0(SP) ; Exit LPM0 on RETI

RETI

 

But if I need set just the GIE bit, how do I do that ?

 

I dont want to use functions like __enable_interrupts(), I

[spirilis 1,265]

The intrinsics are used... e.g.

 

__bis_SR_register(GIE);  // set GIE bit

__bic_SR_register(GIE);  // clear GIE bit

 

Those work in MSPGCC, along with a few variations like _BIS_SR() and _BIC_SR() which might also work in TI's CCS IDE (not sure which one is supported by which though; I always use the __bic_SR_register() and __bis_SR_register() type of intrinsics since I use MSPGCC exclusively)

[spirilis 1,265]

PS, the headers have macros to enter LPMx modes, so here's how I typically do it:

 

_EINT();  // intrinsic to set the GIE bit in SR

LPM0;   // msp430.h header macro that bis's the SR with LPM0_bits

[vadimVladimir 0]

Thanks for reply, but I

[RobG 1,892]

__asm(" BIC.W #0x0008,SR");

__asm(" BIS.W #0x0008,SR");

[spirilis 1,265]

Leave C functions for C programs, or use ASM like Rob's example. Fwiw the compiler condenses the intrinsic functions for the SR down to simple ASM operations against the SR register anyhow.

 

Sent from my Galaxy Note II with Tapatalk 4

 

 

[roadrunner84 466]

Thanks for reply, but I

[vadimVladimir 0]

Love you guys, thanks for all replies !  :thumbup:

[vadimVladimir 0]

Another noob question: People is there a way to power the launchpad (msp430 rev1.5) with a external power and connect to usb only to send uart data ?

 

thanks again.

[piglet 14]

You can supply 5v & ground to the test points TP1 and TP3 beside the USB socket. 

 

If you really don't want to power from the USB then you might have to doctor the micro-usb cable to remove the +5v pin (or cut the wire).  The only time I've had to do that was on a Raspberry pi - to prevent a badly regulated powered USB hub from back-powering the Pi.

[roadrunner84 466]

Remove the vcc , reset and test jumpers from the jumper patch.

The uart/programmer is still powered over usb, but not the msp itself.

[piglet 14]

Where's ground connected if you do that?

 

I interpreted the original post as needing the entire launchpad powered.  It's got to be easier to do that than to put 1.8->3.6v to the launchpad side.

[roadrunner84 466]

ground cannot be disconnected and is required to be connected for correct uart operations.

however, since vcc is disconnected, the msp will only share the zero voltage reference through ground, but will not draw current from usb.

[vadimVladimir 0]

Remove the vcc , reset and test jumpers from the jumper patch.

The uart/programmer is still powered over usb, but not the msp itself.

Thanks again for your help. But do You know any doc where I can learn how the jumpers work ?

 

thanks.

[roadrunner84 466]

On the product page of the launchpad is a document with the schematic.

Basically there are just a few connections from the debugger/emulator to the target msp, by disconnecting these, you cause the msp to run separate.