Features, Applications The MC145557, MC145564, and MC145567 are all per channel PCM Codec­Filters. These devices perform the voice digitization and reconstruction as well as the band limiting and smoothing required for PCM systems. They are designed to operate in both synchronous and asynchronous applications and contain an on­chip precision voltage reference. The MC145554 (Mu­Law) and MC145557 (A­Law) are general purpose devices that are offered in 16­pin packages. The MC145564 (Mu­Law) and MC145567 (A­Law), offered in 20­pin packages, add the capability of analog loopback and push­pull power amplifiers with adjustable gain. These devices have an input operational amplifier whose output is the input to the encoder section.

The IDT821024 is a single-chip, four channel PCM CODEC with on- chip filters. The transmit PCM interface clocks out 1 byte (8 bits) PCM data out of. A bandwidth of 24 kHz (comparable to a PCM system sampled at 48 kHz), a master clock frequency of 3.072 MHz is needed. The one-bit data is asserted on the data line on either the rising or falling edge of the master clock. Most PDM microphones support stereo operation, in which one microphone asserts the data line on the rising. Download rkfree exe shared.

The encoder section immediately low­pass filters the analog signal with an active R­C filter to eliminate very­high­frequency noise from being modulated down to the pass band by the switched capacitor filter. From the active R­C filter, the analog signal is converted to a differential signal. From this point, all analog signal processing is done differentially. This allows processing of an analog signal that is twice the amplitude allowed by a single­ended design, which reduces the significance of noise to both the inverted and non­inverted signal paths.

Another advantage of this differential design is that noise injected via the power supplies is a common­mode signal that is cancelled when the inverted and non­inverted signals are recombined. This dramatically improves the power supply rejection ratio. After the differential converter, a differential switched capacitor filter band passes the analog signal from 3400 Hz before the signal is digitized by the differential compressing A/D converter. The decoder accepts PCM data and expands it using a differential D/A converter. The output of the D/A is low­pass filtered 3400 Hz and sinX/X compensated by a differential switched capacitor filter. The signal is then filtered by an active R­C filter to eliminate the out­of­band energy of the switched capacitor filter.

These PCM Codec­Filters accept both long­frame and short­frame industry standard clock formats. They also maintain compatibility with Motorola's family of TSACs and MC3419/MC34120 SLIC products. The MC145554/57/64/67 family of PCM Codec­Filters utilizes CMOS due to its reliable low­power performance and proven capability for complex analog/digital VLSI functions.

I am working on a custom board based on Freescale iMX6 and Wl1831 to realize an audio streaming application. Host processor is connect to bluetooth chip via UART HCI and also uses PCM lines to connect to wl1831 codec as suggested by TI hardware guide. The problem is that wl1831 PCM is not moving any clock/FSync line. I would like to stream audio from host processor to wl1831 using PCM interface. My setup is the following: - bluez 5.31 - pulseaudio 6.0 - ti wl18xx driver and firmware 8.5R, TIInit_11.8.32.bts file - kernel 3.0.35, with alsa support and bt-sco audio codec With such setup, I am able to pair and connect to heasets or any mobile phone with HFP/HSP.

So I think Bluetooth stack is ok, firmware file is fine and driver is working ok. After connection to such devices with A2DP profile, when I try to play a sample file via paplay, the command stucks, as if the output is not produced waiting for something. Indeed, I checked with oscilloscope that wl1831 codec is not moving clock line, which is needed by bt-sco card codec driver to send PCM samples, since host processor is configured in PCM slave mode. * Question: can you please confirm that wl1831 is configured as PCM master by default? I think it is, because if I enable loopback mode and see clock generate, but when I disable loopback mode it stops. So I need your confirmation. * Question: why wl1831 is not generating clock during bluetooth connection to headsets?

Can you confirm that PCM audio path is enabled by default? Thanks for help. In reply to: Hi Gigi. Thank you for prompt reply. I have some questions: * Can you please describe difference between A2DP and HFP, shortly? I thought they are the same, used for headsets. * About A2DP, is it possible to use PCM lines, somehow?

* About HFP and HCI_VS_Write_CODEC_Config command: ** do you confirm that without this command PCM is silent, while giving it PCM becomes master active? ** how can I read current configuration? ** which values do you suggest for typical application? Sorry for all these questions, but this part is not well documented on TI wiki. In reply to: Hi Federico, * Yes, both are used for Headsets. A2DP is used for media streaming and HFP is used for call audio * There is an option, it is called Assisted A2DP (A3DP - TI specific).