ADAU1467 EVAL BOARD I2C CONNECTION

Question

I got EVAL-ADAU1467Z REV B board recently. I have couple of problems: 
 1- I need circuit schematics of this board. 
 2- I 'm able to load and run ADAU1467 by MCU via SPI connection. it seems analog outputs of AD1937 is fine with sampling rate 48Khz. I need to increase sampling rate 192KHz. To get correct signal at CODEC outputs I need to change register settings of AD1937 as well. I made connection J6/1(SCL) and J6/3(SDA) to MCU. S2 switch is CODEC BOOT MODE. Unfortunately I Have not able to read register contents of AD1937 nor abble to write AD1937 registers. I realy dont understand what 's missing. 
 3- Do I have to set some registers on ADAU1467 to communicate between MCU and AD1937 ,it helps if there's sample code for AD1937 I2C communication 
 
 Kind Regards,

Ken.M · Accepted Answer

Husnu, 
 I have reproduced your problem. It seems that you have uncovered a silicon bug of which we were not aware. 
 I didn't realize that you were using the START_PULSE setting to control the sample rate. While this works under most conditions (when clock master), it requires changing all of the SPORT settings, as well, which I hadn't noticed that you had done. I prefer to change the sample rate to 192 kHz by changing the CLKGEN1 ratio to 2/3 and leaving the SPORT settings alone. Your project was correct there, though. That was not the problem. 
 As you suspected, the issue has to do with the SDATAIOx input missing timing and dropping a bit. It is fine at 96 kHz, but it fails at 192 kHz. The root cause is that the DSP is not making timing on the SDATAIOx input pins at high frequencies. They work fine as outputs, and the primary SDATA pins are fine. 
 However, I have found a workaround (hack) for using 192 kHz on the second input on the eval board. That may or may not work in all systems, but it will get you running. 
 
 Change the output mode of the ADC from I2S mode to left justified mode. This can be done when setting up the CODEC. Initialize the ADCCTRL1 register (address 15) to 0x04 instead of 0x00. The SDATAIO input needs this mismatch to catch the lost bit. 
 Set input SPORT2 to use I2S mode as before. 
 Immediately after the input, multiply the SDATA input by 0.5 (or right shift by one). This will correct for the LJ->I2S mismatch that left shifts by one. 
 Important: Do not use inputs signals that would lead to > -6dBFS input on the SDATA pin since it comes in one bit too hot. 
 
 This is, of course, a rather ugly hack, but it will work. In a real system, you should use an SDATA pin for faster serial inputs rather than SDATAIOx. The biggest downside to this workaround is that the signal on the SDATA pin effectively loses one bit of dynamic range. 
 I've attached a project that incorporates all of this. i don't have a uC setup, so it uses the master control port as in my earlier example. I'm very surprised that this was not discovered during silicon validation or in the six years since this product was released. There is no plan to revise the silicon. 
 I apologize for the trouble. Please let me know if you have more questions. 
 Ken 
 Example EVAL-ADAU1467Z with 192 kHz inputs.zip)

DaveThib · Answer

Hello Husnu, 
 We have a more complete answer for you with examples soon. But let me jump in here to answer some things. 
 Here is the schematics: 
 PDF 
 Question 2: 
 The AD1937 is tied to MP24 and MP25 of the DSP. These pins can be set to be the master I2C port. This is to allow the DSP to control and boot up other parts. This is a different I2C port from the slave port. So your MCU is probably connected to the slave port so as to communicate with the DSP. So you will not be able to communicate with the codec that is on another I2C port. So I think that may be the issue here. 
 You can jumper over the I2C lines to the slave port but then you have to change the slave port over to I2C and that is not easy. So the best route is to actually use the DSP to boot up the codec. We will have details on doing that soon. 
 Dave T

Husnu · Answer

Thanks David 
 My MCU is connected to J6 port on EVAL board. When I set S2 switch to I2C position I'm able read and write codec. But superior solution will be your advice which DSP will read and write codec. I'll look for examples you will provide soon. Thanks ya lot.

Harishgowtham · Answer

Hello Husnu, 
 Regarding the serial port configuration of ADAU1467 Eval board : Like Dave said you can use output channels 4&5,8&9,12&13 and input channels 36&37 with proper serial port setup.Here I have included a project with all set serial ports (input and output channels) of ADAU1467.Hope it will be useful for you. 
 Thanks David for your support. ADAU1467 s.port example for eval board 08-048585.dspproj 
 Thanks & Regards, 
 Harish

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ADAU1467 EVAL BOARD I2C CONNECTION

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