PurePath BiQuadFade question

Bruce12833

Prodigy 80 points

I am trying to use the BiQuadFade component (through SPI). When I set the Enable Transfer

flag address (0x0c on my process flow) I am expecting to see this address go to zero after the

transfer is complete. What I see is this address staying at 0x80. Is there some setup I am missing?

Thanks.

over 16 years ago

0 J- over 16 years ago

TI__Mastermind 46195 points

Bruce,

You need to switch buffers for SPI/I2C to have access to the buffer that the miniDSP had access to.

Once loaded in PPS, you can use the Command-line interface of AIC3254 CS to execute the script below, which will first set the coefficients and then fade them.

Once you finish, you'll notice that if you swap buffers without writing any coefficients, the fade enable coefficient will return to 0x000000.

# Switch to page 44

w 30 00 2c

##########################################################

b "-6dB Gain coeffs will be written and buffers will be swapped"

# -6dB Gain Coefficients

w 30 08 00 00 00 00 40 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

# Switch Buffers

w 30 00 2c 05

##########################################################

b "0dB Gain coeffs will be written and buffers will be swapped"

# 0dB Gain Coefficients

w 30 08 00 00 00 00 7f ff ff 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

# Switch Buffers

w 30 00 2c 05

##########################################################

b "Fade into -6dB Gain"

# Enable Fade

w 30 08 80 00 00 00

# Switch Buffers

w 30 00 2c 05

##########################################################

b "Fade into 0dB Gain"

# Enable Fade

w 30 08 80 00 00 00

# Switch Buffers

w 30 00 2c 05

0 Bruce12833 over 16 years ago in reply to J-

Prodigy 80 points

Thanks,

Sorry to keep pestering you. I am now able to get strange sounds and seem to be effecting the control. I still

have a few questions. First, I am assuming that you meant to write 20 bytes and not 24 bytes in your example?

And secondly, is your example what I need to do for initialization? My control exists at address 12 for the 4 bytes

of flag, and address 16 for the 20 bytes of coefficient. If I understand you correctly I would set the coefficient registers at

address 8, switch buffers, set the coefficient registers again at 8. And then I would use the component interface

at address 12 and 16?

0 J- over 16 years ago in reply to Bruce12833

TI__Mastermind 46195 points

Bruce,

In the script above, 0x08 is the register address for the enable coefficient, 0x0c is for the first biquad coefficient. So in your case I think it the enable starts in 0x0c.

In the script above I wrote to the enable coefficient when I wrote the biquad coefficents (24 bytes). You can write 20 bytes also if you wish. The script below uses the coefficient addresses of your process flow.

A biquad filter with N0 as 0x400000 and the rest of the coefficients as zero, is the same as decreasing the gain by half (in 1.23 format, of course). 0x7FFFFF is close to unity gain. This is a simple exercise for the biquad fade component.

# Switch to page 44

w 30 00 2c

##########################################################

b "-6dB Gain coeffs will be written and buffers will be swapped"

# -6dB Gain Coefficients

w 30 10 40 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

# Switch Buffers

w 30 00 2c 05

##########################################################

b "0dB Gain coeffs will be written and buffers will be swapped"

# 0dB Gain Coefficients

w 30 10 7f ff ff 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

# Switch Buffers

w 30 00 2c 05

##########################################################

b "Fade into -6dB Gain"

# Enable Fade

w 30 0c 80 00 00 00

# Switch Buffers

w 30 00 2c 05

##########################################################

b "Fade into 0dB Gain"

# Enable Fade

w 30 0c 80 00 00 00

# Switch Buffers

w 30 00 2c 05

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PurePath BiQuadFade question