In article <NKudnf_Nhs_jwPnXnZ2dnUVZ_sidnZ2d@giganews.com>,
nick.kani@gmail.com says...
> Hey everyone, I'm working with an MSP430f2012 chip and am tryign to
> generate a delta sigma bitstream using a gpio pin. Unfortunatly whenever I
> try to toggle the pin at a rate faster than 10kHz, the pin appears to not
> be able to fully rise or fall. But isn't 100 us a little slow for rise/fall
> times. Is there any way I can make i t rise/fall faster. At the current
> moment I'm leaving the pins unattached to anything and just measuring the
> output on an oscilloscope.
>
>
>
Are you sure that you don't have the pull-up/pull-down resistors enabled
instead of the outputs?
IIRC, if you do that, then switching the port output simply changes
from the pull-up to the pull-down resistors. That would explain the
slow rise and fall times, as the resistors are about 35K Ohms.
That part has a bunch of other logic on Port 1 with the comparator
inputs, so it looks like there are some extra possibilities for
setting up the port improperly.
I ran into similar problems on an MSP43F248 when I was programming the
pullup and port output to do a bit-banged open-collector emulation
for an I2C port.
Mark Borgerson
Reply by larwe●July 20, 20092009-07-20
On Jul 20, 8:05=A0am, "TheJokerV" <nick.k...@gmail.com> wrote:
> Hey everyone, I'm working with an MSP430f2012 chip and am tryign to
> generate a delta sigma bitstream using a gpio pin. Unfortunatly whenever =
I
> try to toggle the pin at a rate faster than 10kHz, the pin appears to not
> be able to fully rise or fall. But isn't 100 us a little slow for rise/fa=
ll
Strange. What clock speed are you running at? Which GPIO is it?
Certainly the 2012 can generate *much* faster data rates (orders of
magnitude), are you using the PWM generator or the SPI peripheral? Are
you testing on the T2012 target board or your own design; if your own,
is the chip's Vcc adequately bypassed?
Reply by TheJokerV●July 20, 20092009-07-20
Hey everyone, I'm working with an MSP430f2012 chip and am tryign to
generate a delta sigma bitstream using a gpio pin. Unfortunatly whenever I
try to toggle the pin at a rate faster than 10kHz, the pin appears to not
be able to fully rise or fall. But isn't 100 us a little slow for rise/fall
times. Is there any way I can make i t rise/fall faster. At the current
moment I'm leaving the pins unattached to anything and just measuring the
output on an oscilloscope.