Texas DSP 2812 and McBSP

Digital Signal Processing

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  • 1. Question about RS code
    Hi, In my research project(Single Carrier-Frequency Domain Equalization), I have a channel decoded data stream which is modulated/demod in QAM64 form. The error is characterized as burst type due to error propagation. Most error burst length is 4 QAM64 symbols. First, I don't want to use interleaving. This is because we want to do a comparative study. Multi-block interleaving will be unfair for the reference OFDM, while interleaving in one block will be unnecessary (or, even worse?) for RS code if RS code uses the same block length. Then, can I use only RS code? I have read some papers and books. All of them say RS code is suitable as outer code because it is nonbinary code. So, my question is: If I use QAM64, which is not binary stream, RS code is very suitable here to me. So, I do not need to use inner channel code, e.g. converlutional code. Right? Can you give me your points? Have you known what applications or papers use only RS code? Thank you very much.
  • 2. RA Code Simulation Problem
    I am simulating RA code now, but i encounter some problems. First problem, about the decoding and decoding schedule. My fisrt reference paper is "Coding theorem for turbo-like codes" But the paper didn't tell any thing about decoding or schedule. So i found a paper on irregular RA Codes and the Hui Jin's Phd Paper. The former told the decoding algorithm(Sum of Product) and the latter told both decoding algorithm and schedule. (In Hui's Phd paper, i found some error on decoding algorithm.) Hui's Schedule is Parity-to-Check Bit-to-Check Check-to-Parity Check-to-Bit Another Schedule is Parallel Schedule Decoding Parity-to-Check Check-to-Bit Bit-to-Check Check-to-Parity Decoding by calculating APP is finished at the last iteration. The Second problem is "What is the definition of the iteration?". It means that to perform all decoding schedule is an iteration? The last problem, the WER and BER. In fact, i can't have the same result with Hui's. I have debugged my computer program for a week. But i still not know what's problem.... Could anyone help me the simulation? Any source code or detail decoding algorithm...etc... I am thankful anyone who reply the problem.
  • 3. minimax and choosing weights
    You only really have control over the ratio of the ripples (peak-peak, not in dB) using the weights. This is controlled by the ratio of the weights, so if you increase all of the weights by a single factor the filter shouldn't change. Therefor if you set one weight to a fixed number, and vary the other, keeping the other parameters fixed, you will see all the possible responses you can get. But ... keep in mind that you may not be able to meet the spec simply by varying the weights.... like if N is the wrong size (strongly tied to wp and ws) you may never meet spec. dirk
  • 4. adding up coefficients
    Hello, Recently I designed my first IIR filter from a 1st orde Butterworth. After implementation it works as it should. My second filter a 2nd order Butterworth is ready on paper. What occured to me is when I add up the coefficients from the 1st order filter the sum = 1. Surprisingly adding up the coefficients of the second order IIR filter the sum is also = 1. Spare me the Math but is this the case for every filter so I can use this as a check method?
  • 5. Unipolar signal + lms or nlms
    Hi All, I need abit of confirmation and explanation if you all please. I have a unipolar signal which is being prewhitened by being put through a NLMS filter (order 16 taps). It has been suggested that I add in a DC-tap. I'm not sure exactly what I'm supposed to do... Do I now have 17 taps, or still 16 taps with the first one being the DC-tap? (Considering the small numebr of taps, does it really matter if I have 16 or 17?!) This DC-tap will be set to 1 initially. Does it remain at 1 throughout? Or does it adapt like the rest of the taps? I think that the reason I need to add in this DC-tap is to take care of some negative values that I am getting in the error signal, though supposedly this DC-tap may make a significant improvement on the error signal... I've tried to search for some literature on this, but I'm obviously not looking up the right keywords! Many thanks Victoria

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.


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?


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 ?


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.

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

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

Dose someone know how to accomplish this task?

Thanks a lot for your answers

3.own api flashing dsp 2812

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.

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


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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