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freeDSP V2.0 (ADAU1452) developement thread
freeDSP V2.0 (ADAU1452) developement thread
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Old 11th September 2018, 05:04 AM   #251
pnielsen3 is offline pnielsen3
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I have decided to use the ADAU1452 and the codec and the same parts on the evaluation board. The CAD program that I have is very limited. I am trying to find a board that is about the size of my shirt pocket. I am at the point of needing hearing aids. I only need one stereo channel. Commercial hearing aids are for people who have lots of money. $4000 Does anyone know if there is a small board that uses the ADAU1452? I will take the output and feed the stereo signal into a Bluetooth transmitter. I am using a phantom Sony mike for the input.

Any help would be helpful. If someone is selling a DSP and codec board? Please let me know. Or send me a link where I can find a solution. I am on Social Security income. So $4000 is a joke.
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Old 11th September 2018, 05:45 AM   #252
Foxx510 is offline Foxx510  Australia
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Originally Posted by pnielsen3 View Post
I have decided to use the ADAU1452...

Any help would be helpful. If someone is selling a DSP and codec board? Please let me know. Or send me a link where I can find a solution. I am on Social Security income. So $4000 is a joke.
Have you looked at the existing open source hearing aid platforms? Tympan RevD and Open community platform for hearing aid algorithm research

Last edited by Foxx510; 11th September 2018 at 05:52 AM.
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Old 28th September 2018, 12:57 PM   #253
JayShoe is offline JayShoe  United States
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freeDSP V2.0 (ADAU1452) developement thread
Originally Posted by Pitrsek View Post
Hey, not sure if the topic is still open, my two cents:
The design is confirmed, and is being actively used and works well. The signal ground signal configuration is good for signal integrity as well as for EMI.
I think it's a good compromise with regards to size and use and emi. the I2c connection offers a possibility for a port expander, if you need GPIO/HW configuration. I do not know if you consider audio bridge port for ribbon cable connection, but if you do, I would not send low voltages over it - contact resistance and crimp quality might byte you. I If your power supplies are good(low flat impedance), your vcc pin is as good as gnd - with regards to SI and EMC. For ribbon cable connectors it's of not much use (1 pin saved), but for stacking bards this can be used to a greater advantage.

Personally I would keep the FreeDSP expansion connector, and create low voltages locally. It's way easier in the end.
Hello Pitrsek, thank you for your response. As you might know I'm designing an audio mixer. My goal is to create a modular system that would allow me to choose and pick different modules based on the inputs and outputs required. Rather than designing an 8x8, 2x4, 6x6, etc board I am looking to modularize the Codec, adc, dac parts so that I can install as little or as many pieces of each part I need for the project.

The idea is that by doing this way I might get some support from the community that would help me move my project along. Also, I envision (and have not realized) some cost savings manufacturing wise. I figured if I were to create 100 pieces of a single modular PCM5242 for example, it would be cheaper than building a 4x board that may or may not be the right specs for any particular user. So ultimately, if I had a stock of 100 PCM5242 boards and a user needed four outputs, then it's easy to sell 2 boards with 2 outputs on each. For users needing 8 outputs they can buy 4 modules. I'm not looking to build a business off this but I need to mass produce this to get the costs down and then sell some to offset that cost. Depending on how much support I get from the community the hardware and or software would be open. That being said, I'm working on a concept for an "Audio Bridge" and then "Modules".

Your response is greatly appreciated. It looks like sending the I2S and I2C lines to the modules over ribbons is OK. But it sounds like you wouldn't recommend the design as drawn in this schematic (see attached)? It sounds like you don't like the idea of sending the low voltages over the ribbon in this way? My only concern about this is now each module will have to have it's own LDO. It's just more parts. Of course I want this to work right but I want each module to be as simple as possible - like a cheap breakout board. If I put an LDO on each module it just adds to the parts on each module. What do you think? Is this schematic acceptable?

PS - I know the "audio bridge port" isn't drawn exactly like the FreeDSP Expansion Connector. Just look at what it's carrying, not it's organization. I think you might have sold me on organizing it with a row of grounds, but I'd like to include the low voltages... Even if I were to have a standard FreeDSP expansion connector and then a second row of 1.8, 3.3, 5.0v, and some GPIO. No? Yes?

PPS - (GPIO is for some extra features in ADC/DAC parts such as a "RESET" in the TLV320AIC3104 or a "XSMT" aka "soft mute" in the PCM5242.)
Attached Files
File Type: pdf TEENSY_BRIDGE_C1.pdf (85.0 KB, 42 views)
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Old 4th October 2018, 07:28 PM   #254
Pitrsek is offline Pitrsek  Czech Republic
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Ribbons, especially in S-G-S-G... are a very fine connection - provided you keep the length reasonable. With I2C bus - keep in mind that there are limits how much capacitance the bus can tolerate - that translates into limit on cable length and/or number of modules.

Local LDO is not a bad thing. Impedance is low, every module has it's own short circuit protection, no crosstalk/dustrubances over the power supply lines. And It's not expansive. If you share LDO for different boards, the total power is limited by your LDO. Your current limit is given by your ability to cool the LDO. Do the calculations, it's not that much... If you let module create it's own voltage, power is limited by the adapter.

What if I need 1.2V, or 6V for some reason? LDO are cheap. IMHO The biggest PITA is the negative voltage for opamps. I would not be too hung up on the parts price/count, if there is few $ in bom, nobody cares(as long as it's not a 1000s series bussines). Place where I used to work had a bad experience with low voltages over ribbon cable(contact resistance).

With regard to GPIO - I was considering providing them on FreeDSP connector, decieded not to based on connector size - would not fit 3x to eurocad board edge, and there is a limited amount of GPIO in ADAU dsp. For most part, I2C is all you need. And if you for some reason really need indpenedend GPIO from the DAC/ADC, i2c port expander is again 1$ in single quantity...
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Old 24th November 2018, 03:51 AM   #255
dmytty is offline dmytty
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I have been working on using a few different concepts which could result in a 'longer bridge' than ribbon cables and thus serve as an extendable interconnect, while also bringing galvanic isolation.

Optical SPDIF ... a working board that could output i2s to the FreeDSP board
CS8416 Source Selector Module 2 SPDIF Inputs to 1 I2S Output - Audiophonics

A few other concepts utilizing AVB (Ethernet) and ADAT optical

XMOS based ADAT encoder/decoder

XMOS ... AVB to I2S
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Old 11th January 2019, 10:18 AM   #256
ojg is offline ojg
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Location: Norway
freeDSP V2.0 (ADAU1452) developement thread
Hi Pitrsek,

Is it possible to update the design files on Github with the B3 version?

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