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AD1937: Failure due to I2C interface
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"quad-buffer" headphone amplifier
AD1835: Output filters
AD1835A: DC offset voltage
AD1836: Sampling at 22.05kHz
AD1845: DC offset
AD1852: ESD sensitivity, HBM model data missing from datasheet
AD1853 EVB
AD1853: output impedance
AD1853: Two devices in parallel
AD1854: SPI port unused
AD1862
AD1871 single ended input range
AD1877: Calculation of the LSB value
AD1896: Configuration
AD1937: Failure due to I2C interface
AD1939
AD1939: datasheet contradictions on SPI timing specification
AD193x family - supporting Sample Rates lower than 32 kHz
AD1955: Independency of the channels
AD1974 Stop Band Filter Response
AD1981 PCB Layout recommendation
AD1981B drivers
AD1981B EVB
AD1986: AC97 code
AD1992: Driving the input stage
AD73311: Power supply
AD73311: Power supply sequencing problem, using DVDD = 3.3V and AVDD = 5.2V
AD73311L: Cascade running at different sampling speeds
AD73322/AD73322L compatibility
AD73322: CD measurability
AD73322: Vref transfer function
AD73322L: Frequency response
AD73360 timing questions
AD73360: Frequency response over sample rate
AD73360: Grounding
AD73360: Lower limit of the MCLK
AD73360: Reference voltage
AD73360: SDOFS in figure 10
AD73360: Settling time when changing the PGA gain
AD73360AR: DC performance
AD73360L: Reference does not always power up
ADAU1761: Can I connect one analog and one digital input channel to the ADAU1761 and process both of them together?
ADAU1966 maximum load current
ADAU1966: If using a direct MCLK can I leave LF and PLLVDD pins disconnected?
AVDD and DVDD range
Binary 2.20 format
Can AD1836A work at 32KHz or 44.1KHz sample rate?
Change sample rate by controlling SE pin.
Clicks and pops on power up
Dejitter issue
Do Analog Devices still have a range of HD Audio Codecs or has this technology all been sold off to Conexant?
Does the AD1852 accept SPDIF format?
Does volume control setting affect THD+N ?
EVAL-ADAU1472Z Evaluation Board support files (public)
EVAL-SSM2518Z evaluation board documentation and DLL for I2C control
Evaluation board Datasheet
FAQ: Can a digital microphone's PDM output be directly connected to an I2S input?
FAQ: Can MEMS mics be soldered to a flex PCB?
FAQ: Is a microphone with higher sensitivity better than one with lower sensitivity?
Gerber files for Eval board
How do I handle unused digital pins on an AD193x codec?
How to connect unused SDATA inputs on ADAU1966?
How to create an EEPROM image for the ADAU1772 that has different filter coefficients in Bank A and Bank B
I2S interface configuration
Interesting microphone application - "Acoustic telescope"
Long term drift for gain, Uref and FIT data
Low latency audio codec
MEMS microphone IBIS models
New MEMS microphone products
Power supplies, capacitors, and application schematics
Ref out voltage of the EVB
REGEN and THERM pins
Replacement for WM8731SEFL
Request for a 32 bit audio codec
Sample rate lower than 32KHz
SigmaStudio Help File - where could I find it
SSM2250: Replacement type available?
SSM2302: Output overshoot.
SSM2306: Exposed pad connection
SSM2529 Evaluation Board Documentation
SSM2529: Evaluation board documentation
SSM2603 audio codec power supply questions
SSM2603/SSM2604 Boot Sequence
Stand-alone Modes on the AD193x audio CODECs
Temperature drift of the internal PGA
The relationship between value of Input Level Control register (Address 0) and gain value
Unused analog input pin connection
Using ADAU1761 for microphone beamforming
Using ADAU1772 for microphone beamforming
Using LRCLK as PLL input
Video: Getting started with the EVAL-ADMP441Z
Video: Microphone Array Beamforming with the ADMP504
Whether it is pin compatible with TI TPA2010, On-Semi NCP2820?
Why doesn't Analog Devices manufacture 32-bit audio converters?
Working at 8KHz sample rate
AD1937: Failure due to I2C interface
Q
We have an audio device built around the ADAU1445-DSP and the AD1937 CODEC.
The ADAU1445-DSP is the clock master.
Both of them are controlled on the same I2C bus by a processor, with a
software, (‘bit bang’), I2C.
7 bit address of the AD1937 is 0x04 and the ADAU1445 is 0x38.
When our processor gets busy, the I2C is a low priority and gets interrupted.
We can see on the oscilloscope that sometimes midway through an I2C
transaction, both the SCL and the SDA ports stay low for about 40ms.
This within the I2C specs as there’s no limit on clock or data speed, the I2C
protocol analyzer, (
http://www.totalphase.com/products/beagle_ism/
), shown no
errors, took us a while to notice the 40ms delay in the transaction.
When this 40ms both signal low happens, the AD1937’s AD clocks lock up:
- Both clock pins, (ALRCLK and ALRCLK), turn from normally configured input to
output,
(and as our system is normally configured as CODEC slave, we have very loud
noise sent on all AD channels with two out of phase clock sources).
- I2C communication is working OK, can write and read all registers.
- Verified, that all written commands into registers are correctly executed,
except the AD clock pin directions, we can even change the ABCLK rate.
Only Hardware reset will release the AD1937 from this locked state. We are
wondering if this problem is known to AD, or you can see something we are
missing, (and possibly on the wrong track).
A
We have done a comprehensive analysis of Stand Alone mode in the AD193x family
of parts. Given the fact that the customer is using the AD1937, I will refer to
the I2C pins, with respect to the corresponding stand alone mode pins.
There are 4 pins total that are used for Stand Alone mode: ADDR0, ADDR1, SCL,
and SDA, see the table 12 n the datasheet.
Usually, it would be assumed that an IC would look at the Stand Alone mode port
once at startup and stay fixed, in or out, of Stand Alone mode until the next
reset. However, it appears from bench testing that the AD1937 will go into
Stand Alone mode if ADDR0, ADDR1 and SCL are all held Low for more than 4 mS,
with the state of SDA setting the ADC Clock ports to Master or Slave. At the
same time, the Stand Alone mode will revert to *default* state if the pin
conditions above are removed.
If the customer is using ADDR 00, two of the three pins are already low. If the
SDA and SCL pins are held low for 40 mS, this would certainly put the part in
Stand Alone Slave mode, and when the SDA and SCL pins come back high, the part
will be left in default. The easiest solution would be to change the I2C
address by pulling either or both ADDR0/1 pins high; the AD1937 will never go
into Stand Alone mode.
P.S. After some lengthy testing, it turns out that the part does not lose its
register settings when it goes into and comes out of Stand Alone mode.
ad1937
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