Texas DSP 2812 and McBSP

Digital Signal Processing

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  • 1. Definition of autocorrelation -- it was obvious but not now
    Hello, Signal Processing Experts, There is something that I have been so used to and does not look so obvious today. On page 98 of Communication Systems Engineering by Proakis (1st edition), it defines the autocorrelation function as the convolution between the signal itself and time reversed version of its complex conjugate: Rx(tau) = x(tau) convolve x*(-tau) --- (1.1) = integral from -inf to +inf { x(t) x*(t-tau) } dt --- (1) However, when we talk about convolution of two signals we always assume that the two signals have the same independent variable, such as what follows that the independent variable is tau: x1(tau) convolve x2(tau) = integral from -inf to +inf { x1(t) x2(tau- t) } dt --- (2) How do we get (1) from (1.1) and (2)? I mean that I just cannot apply the definition of convolution in (2) to (1.1) since the second function in the convolution in (1.1) does not have the same independent variable as the first function -- the first one is tau, the second one is -tau. Could anyone help me with this? Thanks, Carl
  • 2. Windowing in the Frequency Domain
    Hello there, I'm currently working on a pitch identification program in MATLAB. It uses the Sliding DFT so I need to apply windowing functions in the frequency domain. I understand this is done by convolution and have managed to find the kernel for the von Hann window: [-0.25 0.5 -0.25], but am struggling to find a concrete answer for other windows like the Hamming and Blackman window. Anyone know? Also, am I right in thinking I should be using the circular convolution (cconv) function to do this in MATLAB? And why doesn't cconv(A,[-0.25 0.5 -0.25]) give a result that's the same size as A? I can't understand where the extra elements come from. Thanks for reading, now wash your hands.
  • 3. interloation algo
    Hi,every one. I read some matlab program (Voicebox - estnoisem.m)and inverse the line to be interloation logo. But I can not tell which kinds kind of interloation it is. y = xi - (xi*xj)/(x-xj) * (yi-yj)/(xi-xj) Whick kinds of interpolation is it? Anyone can tell it? Thank you. The refered matlab line is as follows. % What is the priciple algo? Where it is described? m=dmh(i,2)+(qi*qj/q-qj)*(dmh(j,2)-dmh(i,2))/(qi-qj); Any comments would be appreciated. Cheers HyeeWang
  • 4. LPF order at DAC output
    Says who? The filter characteristics (and hence it's order) should be derived from an understanding of the problem. It sounds like you're applying a cookbook solution that is not only narrow and simplistic, but very possibly wrong in many cases. The filter order does depend on the ADC. If a 12-bit ADC is chosen having an attenuation in stop band of less than 72dB will ensure that the unwanted frequency band does not occupy even one bit of ADC. Same way for pass-band ripple.
  • 5. Programmable Low Pass Filter
    Hi all I am currently working on a diversity combiner for a FPGA based receiver system. The design calls for a programmable LP filter. Till now I have just used the MatLab Filter VHDL generator for fixed filters. I understand that a variable decimator can be used with a fixed low pass filter to effectively create a programmable low pass filter. I am unsure of the theory behind this. Any guidance as to whether this combination will work (would an interpolator be needed also?), and how it might be built in VHDL would be greatly appreciated. Kind regards, Kurt

Texas DSP 2812 and McBSP

Postby Torgeir Jakobsen » Thu, 02 Dec 2004 02:40:47 GMT

Hi all DSP experts :-)

I have a problem with the McBSP receive interrupt on the 2812 DSP from
Texas. Do anyone have working code on this DSP ?
I have done much the same as on the 5510 DSP where I did not have this
problem, so I do not understand why it is not working here ?

Thanks in advance.

Torgeir



Re: Texas DSP 2812 and McBSP

Postby Brad Griffis » Thu, 02 Dec 2004 10:44:32 GMT

There are more things you need to enable to get interrupts on the 2812 than 
there are on the 5510.  Are you sure that you have enabled the PIE, set the 
proper bit in the PIEIER for the McBSP interrupt, acknowledged the PIE 
(PIEACK), set the corresponding IER bit, and cleared the INTM bit?

Also, are you sure that you have configured the McBSP to generate a receive 
interrupt?  Are you seeing the RRDY flag which indicates there is data in 
the McBSP to be read?

Brad








Re: Texas DSP 2812 and McBSP

Postby Torgeir Jakobsen » Thu, 02 Dec 2004 18:55:30 GMT

Thank you Brad,

I have done the things you describe:
- Enabled PIE
- Set PIEIER for McBSP receive interrupt
- Acknowledged the PIE
- Set IER
- Cleared INTM.

First it looked like RRDY was not set, but now the RRDY is set. I have also
enabled the transmit interrupt to see if this was working better.  I can see
that RRDY and XRDY is set but the PIEIFR register (and PIEACK) does not flag
any interrupt, even if McBSP is set to generate interrupt on RRDY and XRDY
and the PIEIER is set to enable both interrupts.
I am using the sample rate generator, and the clock and frame signals are
generated correctly (measured with oscilloscope).

Any suggestions ?






than
the
receive






Similar Threads:

1.McBSP interrupts on Texas 2812

I have problems with the receive and transmit interrupts on this DSP. I have
set the McBSP to generate interrupts on RRDY and XRDY, and I can see that
these bits are set when I emulate the program on my hardware (using XDS510PP
Plus and CCS). This should also have activated the corresponding interrupt
flags in the PIEIFR6 regsiter (bit 5 and 6), but this does not happen.
I can see that my ISRs are working if I set the interrupt flags in PIEIFR6
manually, so the problem is the connection between the McBSP and the PIEIFR6
register. What do I have to do to make the McBSP RRDY and XRDY activate the
flags in PIEIFR6 ?
I use the internal sample rate generator, and I can see the frame and clock
signals with my oscilloscope.

Thank you in advance.

2.hwo to set up interrupt in dsp 2812

Hi everyone!
I am new in using dsp 2812.

I want to make an T3PINT interrupt.

I just read "TMS320x281x DSP System Control and Interrupts Reference
Guide"(spru078e) and
"TMS320x281x DSP Event Manager (EV) Reference Guide"(spru065e),

On page 84 in spru065e,and on page 122 in spru078e,
what's mentioned in the priority field seems different.
Why?

I am traceing the C of the example "sw_prioritized_interrupts"
mentioned in the document "C281x C/C++ Header Files and Peripheral
Examples".

It seems that cpu branchs to ISR to setup priority.Is this the way it
does? Or Is my understanding wrong?
(FILE:   DSP281x_SWPiroritizedPieVect.c)

If priority can be set in code,why priority are mentioned in these
document?

Dose someone know how to accomplish this task?

Thanks a lot for your answers
Bell

3.own api flashing dsp 2812

Hello,
I work on  a 2812 dsp board, I make a c# application to test it and now 
want to flash it.

On this board i have four Dsp (not interconnected), i use SDFlash wit
four com port and four sdp project.

I can create a process which will launch four SDFlash.
Does SdFlash can take arguments in a command line, like this ?
\SdFlash clientprjCom1.sdp
...
\SdFlash clientprjCom4.sdp

An other idea is to create my own window working like SDFlash.
In this case, do you know if it's possible to have SDFlash source code
or informations about c++ input methods that i can call to flash dsp.

A last question, does it exist an industrial method to flash more fastly
several dsp.

thank you for your help.
Laurence




4.ADC's noise on DSP 2812

Hi everybody !!!

Can someone help me to solve the following problem ?
I need to use an external signal in my program in order to make a goo
enslavment of a signal.
So what, i want to get a very accurate value of my external signal.
I use the ADC module of the DSP 2812 but when I look a the value returne
there's a lot of noise on it.
Can someone explain me why this measure is so noisy and how i coul
improve it ?
Thanks a lot

Laurence

5.DSP-2812: Calling SCI_BOOT from the program

Hi All,

I want to call SCI_BOOT in my program in order to use SDFlash to update
the flash. The resistors are set up in such a way that it boots from
flash and I don't want to change that. Or can the DSP-resetted in such
a way that it ignores the hardware and boots from SCI_BOOT anyway.

Kind regards, Frank

6. Matlab GUI for coupling TI 2812 DSP with Simulink RTW

7. ADC using 2812

8. flash and external ram timing on TI 2812



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