Help setting port pins before initializing global variables for MSP430F5635

Try using _system_pre_init(void).

Regards,
Maciej 

Hi!

Thanks for the reply. We tried using _system_pre_init() but even with this we are seeing the port pin go high for about 1ms approximately 3 ms after the controller gets power.

-Aparikh

Hi,

have you tried also to switch of the watchdog timer in the system pre init function ?

http://processors.wiki.ti.com/index.php/MSP430_FAQ#WDT_fires_during_C_startup_code

Hi,

Yes, I am stopping the watchdog timer first in system pre init before setting the port pins.

-Aparikh

Aparikh,

can you share your system pre init function? do you give a "1" as return value in the system pre init function? You need it for initializing your global and static variables.

http://processors.wiki.ti.com/index.php/MSP430_FAQ#Is_it_possible_to_retrieve_the_cause_of_a_reset.3F

I once made this mistake and it really took me a lot of time to find the problem cause.

Hi Leo,

Yes, I am returning a 1. Here is the snippet -

int _system_pre_init(void)
{
  WDTCTL = WDTPW+WDTHOLD;                   // Stop watchdog timer

  P8DIR |= BIT0;
  P5DIR |= BIT5;
  P1DIR |= BIT3;
  P9DIR = 0xFF;
  P1DIR |= BIT0;    

  P5OUT |= BIT5;
  P1OUT &= ~BIT3;
  P8OUT |= BIT0;
  P5OUT &= ~BIT5;
  P9OUT = 0x00;
  P1OUT &= ~BIT0;
 
  return (1);
}

Hi Amee,

i think i have misunderstood your question, sorry for that.

Please notice that after reset all GPIO should be set as input, so i wonder why you see the pin goes high (unless you have a pull-up resistor connected to the pin).

Another thing is that after reset, the first thing which will run is the boot code. It will do some device initialization and decide whether to run the BSL or the application code. If you want to shorten things, maybe you can do the following if you don't need the BSL: erase the BSL, or the BSL signature at address 0x17F4-0x17F7. Please refer here: http://processors.wiki.ti.com/index.php/Custom_MSP430_BSL#Device_Startup_Sequence.

Please notice that BSL access is per default disabled: http://processors.wiki.ti.com/index.php/MSP430_FAQ#How_to_enable_the_access_to_BSL_Flash_memory_in_MSP430F5xx.2F6xx_devices_.3F

Hi Leo,

Thanks for that link. But here the thing that Im worried about is that the BSL should take usec whereas im seeing almost 4 msec before the port pins are getting set in system pre init. Any idea what could be the reason for this long a delay??

Thanks in advance.

-Aparikh

You should check datasheet because your 4 ms might be Power On Reset + Brown Out Reset + Power Up Clear time.

Regards,
Maciej 

Amee Parikh said:

As a result, some of the port pins go high for 30ms before they are set to low in main().

This is a hardware problem that can't be fixed in sw. On reset IO pins will float.

If low voltage is to be guaranteed, then you must add external pulldown resistors. (100k to 1M ) 

Peter

Peter Dvorak said:

This is a hardware problem that can't be fixed in sw. On reset IO pins will float.

But not for 30ms. The datasheet gives 2-3ms from RST going high to execution of the reset vector. The no-init function should be executed only a few µs later. Also, the port pin reset won't likely happen right at the start of these 2-3ms.

Peter Dvorak said:

If low voltage is to be guaranteed, then you must add external pulldown resistors. (100k to 1M ) 

Indeed, if you need any I/O having a specific active level at CPU startup, then external pullups or pulldowns ar mandatory.