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TDA1540 - I2S to Offset Binary, no CPLD, no FPGA
TDA1540 - I2S to Offset Binary, no CPLD, no FPGA
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Old 15th August 2019, 05:30 AM   #1
miro1360 is offline miro1360  Europe
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Default TDA1540 - I2S to Offset Binary, no CPLD, no FPGA

Hi folks,

my first attempt for converting I2S to Offset Binary. This format is used in the old 14-bit R2R DAC chip TDA1540.
The conversion from I2S to Offset Binary is as simple as inverting the MSB bit. It is easier said than done
My logic is created from naked logic gates and a few shift registers. It is working for the standard I2S word in length of 64 bits (generated from well known XMOS based converters, or PCM2706/7).

Basic principle:
- MSB bit is inverted after each LRCK edge, controlled by XOR gate + pulse
- BCK is inverted for TDA1540, and used for shift registers for better timing
- DATA are shifted, aligned for left and right channel, latched together in 14-bits and the rest of unusable data are ignored
- LATCH is generated after each LRCK cycle
Note: instead of NOT and AND gates are many NAND gates used (6 NAND gates in one chip).

Converting serial to parallel - inverting bit - parallel back to serial seems be hungry for parts, so I did it very simple, simple but not perfect. There is no synchronization and maybe a hidden timing issue.

Any improvements are welcome, like stop clock operation for both channels, better timing, ...


Test + Schematic
Attached Images
File Type: jpg TDA1540-I2S_miro1360.jpg (651.2 KB, 168 views)
File Type: jpg TDA1540_logic.jpg (62.9 KB, 166 views)

Last edited by miro1360; 8th October 2019 at 10:45 AM.
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Old 15th August 2019, 06:29 AM   #2
Zoran is offline Zoran  Serbia
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Hi Miro1360
Stopped clock will be welcome?
.
btw
And what about 1540 sound?
I like it very much.
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Old 15th August 2019, 03:25 PM   #3
miro1360 is offline miro1360  Europe
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An experienced engineer named Nemo (from another forum) told me, that the stopped clock will be desirable because it avoids possible collisions. Digital filter SAA7030 used among with TDA1540 stopped the clock for both channels.
I can't say much about the sound because I didn't make any active comparisons yet.
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Old 16th August 2019, 04:57 AM   #4
miro1360 is offline miro1360  Europe
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Here is the stopped clock and MSB inverter from the experienced engineer Nemo:
Click the image to open in full size.
Far advanced design (the first one on the image is for standard I2S)
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Old 17th August 2019, 10:20 PM   #5
Zoran is offline Zoran  Serbia
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Join Date: Jan 2004
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Quote:
Originally Posted by miro1360 View Post
Here is the stopped clock and MSB inverter from the experienced engineer Nemo:
Click the image to open in full size.
Far advanced design (the first one on the image is for standard I2S)
It is look a like design for Altera chip?

(BTW I am running 1540 with i2s-ST with xilinx cpld. I was amazed with 384KHz operation and 20KHz square whale out...)
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Old 17th August 2019, 11:21 PM   #6
miro1360 is offline miro1360  Europe
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This design is not working with Altera. With any cpld or fpga it has to be synchronized (from master clock), perhaps about what you did with xilinx. Nemo also has a design for synchronized CPLD (purely schema-based), but I have no right to publish it. One can find him and ask him privately.
I will test this stopped clock from basic logic elements on breadboard and if it works, I will make it as a DAC powered from USB for my collection.

Last edited by miro1360; 17th August 2019 at 11:23 PM.
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Old 7th September 2019, 08:29 AM   #7
Viking RB is offline Viking RB
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Default Hi

I need a good function schematic for the Tda1540. Preferably i2s to Simultaneous Data 14bit.
Also i want to be able to use a saa 7030 to togle between NOS and OS (although this is something i can work on.) please help me out! I've tried everything. Kinda wanna stay on the ic side too.
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Old 10th September 2019, 06:49 PM   #8
Zoran is offline Zoran  Serbia
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Join Date: Jan 2004
Location: Belgrade
Quote:
Originally Posted by Viking RB View Post
I need a good function schematic for the Tda1540. Preferably i2s to Simultaneous Data 14bit.
Also i want to be able to use a saa 7030 to togle between NOS and OS (although this is something i can work on.) please help me out! I've tried everything. Kinda wanna stay on the ic side too.
From another thread:
Building the ultimate NOS DAC using TDA1541A
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