I built that board but didn't debug it or finish off any of the software, so I'm not sure that it works. I'll return to it when I try to build a final version of the 4-channel amp module. I decided to use the Midiworx 8-channel SSM3582 boards for a line array prototype, so testing and writing code for this board got put on hold (see blog on Audiodevelopers.com). The Kicad files are attached. Here is a fuzzy picture of the assembled but untested board (sorry about the focus):
You asked for this board with the Linkplay A31, but I would recommend using a newer version of the ADAU1466 board shown in the Audiodevelopers blog instead. The reason is that it has the SPDIF (TOSLINK) input for using the Wiim Mini, which is a great improvement over the A31 technology. There are two versions of that board now. The 1st version is for the line array, with connectors for 24 channels of audio. The 2nd version is intended as a stereo 3-way board that connects directly to the Wondom/Sure TAS5756 board via I2S. That should make a nice active speaker. I'm still awaiting some parts, but I'll be testing those designs soon.
BTW, You can sometimes get "refurbished" Wiim Mini's on Ebay for $59: https://www.ebay.com/itm/125642191250.
BTW, You can sometimes get "refurbished" Wiim Mini's on Ebay for $59: https://www.ebay.com/itm/125642191250.
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Neil Said: "The 2nd version is intended as a stereo 3-way board that connects directly to the Wondom/Sure TAS5756 board via I2S." An alternative I2S amp is a MA12070P amplifier. I use this one with a 1452 board via I2S:
https://www.aliexpress.us/item/3256...st_main.5.37f418029dUrKc&gatewayAdapt=glo2usa
https://www.aliexpress.us/item/3256...st_main.5.37f418029dUrKc&gatewayAdapt=glo2usa
The MA12070P amp uses a different pinout for the I2S connection, but if I make another iteration of this board, I'll include connectors for both of these amps 
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I like this board, and I might end up making another version. The only thing I don't like is that it's a little cumbersome to switch between the two TOSLINK inputs. The SPDIF switch is controlled by the ESP32 via a phone app, and I should probably add a way to "manually" select the inputs. I use one TOSLINK input for the Wiim Mini and the other is for an HDMI audio extractor that grabs the SPDIF signal from the connection to the PC monitor. Windows controls the HDMI audio volume, and it is very convenient to control the volume from the Windows keyboard. The more I use HDMI audio the more I like it. Wondom offers a small amp with a built-in HDMI extractor--I think this will be a trend.
.I like this board, and I might end up making another version. The only thing I don't like is that it's a little cumbersome to switch between the two TOSLINK inputs. The SPDIF switch is controlled by the ESP32 via a phone app, and I should probably add a way to "manually" select the inputs. I use one TOSLINK input for the Wiim Mini and the other is for an HDMI audio extractor that grabs the SPDIF signal from the connection to the PC monitor. Windows controls the HDMI audio volume, and it is very convenient to control the volume from the Windows keyboard. The more I use HDMI audio the more I like it. Wondom offers a small amp with a built-in HDMI extractor--I think this will be a trend.
Appreciated, and appreciate the files as well, but my use case is probably very different from most.
I'm just looking to use the Linkplay board to interface with HomeAssistant for a LOCALLY controlled smart speaker. Something I can hook up to ethernet (and most likely POE powered), and send low quality alert chimes/sound clips to. I have it all working on a breadboard, just looking to fab a proper PCB and really didn't want to reinvent the wheel and draw the A31 footprint if I didn't need to!
This github project has in-depth technical info about the Linkplay A31 module and also describes how to replace the vendor firmware with a (OpenWrt) Linux system (I2S slave mode).
There is also some information on how to dump and modify the firmware of the MVsilicon AP8064 MCU, which is often used as a complement to the A31 module.
Hope this is of interest to someone
There is also some information on how to dump and modify the firmware of the MVsilicon AP8064 MCU, which is often used as a complement to the A31 module.
Hope this is of interest to someone
192/24 is a tall order for a 10-year-old MCU that only supports 802.11a/b/n wireless networking. According to speedguide.net, you would probably need dual antennas and a quiet environment to support the sustained 12MHz data rate needed for 192/24. The work with the Linkplay A31 is interesting and impressive, but it's going to be limited by the Mediatek MT7688AN platform.
I've got a pair of A98 modules that I don't need. If anyone is serious about developing firmware for it, they are welcome to have one for free.
I've got a pair of A98 modules that I don't need. If anyone is serious about developing firmware for it, they are welcome to have one for free.
Problably not a trivial task. From my understanding, for master mode, you'd at least need to add a codec (other systems use the Wolfson WM8960 connected via I2C, see https://github.com/openwrt/openwrt/blob/main/target/linux/ramips/dts/mt7628an_duzun_dm06.dts for an example). I have no idea if higher data rates would be possible (@Neil Davis I think the high data rate is needed on the I2S link only as the mp3 is decoded on the MCU -- so no high data rate is needed on the WiFi connection),
I am neither an I2S nor an audio expert. The project started with the goal of removing the annoying welcome message and coincidentally ended with replacing/modifying the fimware on these two MCUs