digital In to EVAL-ADAU1701
Hi everybody,
I'm trying to interface an eval-adau1701 board with an external SPDIF receiver.
According to the documentation of the board I'm using header J7, where all digital signals can be connected:
"EXTERNAL DIGITAL AUDIO INPUT
To use the digital audio input port of the ADAU1701, the
serial data, BCLK, and LRCLK signals must be connected to
an external source using Header J7. The source needs to be
synchronous to the ADAU1701, thus, the MCLK should be
input to this header as well. On J7, the row of pins along the
edge of the board are ground and the inner row of pins are
the signals.
Within the SigmaStudio software, the digital input Channel 0
through Channel 7 are accessed in the input cell in Position 2
through Position 9, as shown in Figure 6. Position 0 and
Position 1 are inputs from the ADCs.
"
I have a SPDIF board using a cs8416 receiver. This outputs left justified data, with a 256*fs MCLK. Fs is 44100 hz, as the data comes from the SPDIF
ouf of a CD player. According to the above description I have connected BCLK, LRCLK, and serial data, and also MCLK to header J7.
Now, problem #1:
you also have to change switch S1 on the board so that MCLK for the chip comes from the header and not from the crystal on board.
What I see is that if I want to compile/link/download a program to the board using the USB link and SigmaDSP interface, the communication fails if the switch S1 is set to use the clock on header J7, while the transfer is OK if I set the switch to use the internal crystal.
I suppose that in this way I can send the software to the board, but then?
Can I switch on the fly to the other position? Do the 1701 accept to change its clock this way maintaining the internal program?
Or am I doing something wrong? What's the correct procedure to use an external clock?
Then, problem #2:
the program don't works. I have a simple program with a volume control and out to the internal dacs, just to test that serial data in is working.
Nothing happens. This can be a consequence of problem #1, but in case that the abowe switching procedure is correct, how can I check
that the chip is actually receiving data from the serial data in?
Thank you for your support.
Audio Signal Processors
input
digital
SigmaDSP Audio Processors
adau1701
1701
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Your project file looks correct. Have you tried actually putting a probe on the MCLKI pin of the ADAU1701 and checking to see if the signal is there? Make sure it's arriving at the pin and shows a solid 12.288 MHz, with an amplitude of around 3.3 V. That's the first step.
There is no special method for clocking the board externally. Technically, you shouldn't be switching clock sources on the fly in a real application, but the PLL is robust enough that if you switch the clock source during operation on the eval board, it should stay locked. So, I'm guessing this might just be an issue with the clock signal actually arriving at the pin.
Yes, the issue is now solved. It was due to the clock that arrived from a CD player, and was present only at intervals.
In any case, when used in situations in which the clock can be present at intervals (i.e. when the clock comes from an SPDIF receiver),
it can happen the clock halts or changes during operation .... I wonder if any document describes what happens in this situations: does the ADAU1701
"freeze" and restarts from where it was, or does it reset when new clock arrives and reloads the program from eprom?
Bye.
When MCLK goes away completely, in my experience you can still write over the I2C port with no problems. You can also re-supply MCLK at a later point and everything should start working again. Although, to be safe, I would suggest resetting the device just to make sure.
The device will not reset and reload the EEPROM contents just by removing MCLK. You need to actually toggle the reset line or remove power in order for that to happen.
This question has been closed by the EZ team and is assumed answered.
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