A collection of data and code to retask various parts of a 2^nd generation Echo.

Instalation instructions are at the end.

The current setup for the microphones means that the data voltage for the TLV320ADC3101 is too high. This is because the audio clocks generated by the Raspberry Pi operate at a levels of 5v and the voltage levels for the TLV320ADC3101 operate at 1.8v. As a result of this the IOVDD and DVDD voltages rise from 1.8v to about 2.3v (measured) which is above the maximum recommended rating of 1.95v but below the absolute maximum of 2.5v. The documentation states that operating above the recommended level could impact device reliability. An appropriate logic level shifter should be used between the Pi and the TLV320ADC3101 but I haven’t yet found one.

The Echo power supply provides 3.8v, but, the LED/Mic board requires 3.8v, 3.3v and 1.8v to correctly function. In addition to this, if you intend to power a Raspberry Pi then 5v is also needed.

In order to facilitate this a DC-DC Buck converter is used to step down the 3.8v to 1.8v and DC-DC Boost converter to step it up to 5v. The 3.3v is provided by the Raspberry Pi.

When using the Echo as the power supply for a Raspberry Pi 4 I had to throttle the Pi to prevent under voltage. This was probably due to the cheap Boost converter I was using.

The LED ring is fully controllable via I²C and a program is provided to show various LED patterns.

At the present moment you can only record from 2 of the 7 microphones.

Unfortunately, the Kernel provided for the Raspberry Pi does not include the driver for the TLV320ADC3101. This means you either have to modify the Kernel config and rebuild it, or copy the source file from the Kernel source tree and compile it independently. I chose the latter since it only take a few minutes as opposed to a few hours.

There is a light sensor on the LED Ring board located by the ACTION button. Based upon its I²C address (0x39) and the response to some I²C queries I believe that this is an OSRAM TSL2540.

The chip used by the amplifier is a TPA3118D2 which is, apparently, an analogue input Class-D audio amplifier. Apart from that, I haven’t investigated the amplifier yet.

These instructions are based upon 64-bit Raspbian Lite OS version 12 (Bookworm).

You will need the following:

• A 1.8v DC-DC Buck converter
• A 5v DC-DC Boost converter (optional)
• A Logic Level Shifter capable of handling I²C
• A 37P 0.3mm pitch FPC/FFC breakout board
• A 24P 0.5mm pitch FPC/FFC breakout board

1. Wire everything up as shown in the Wiring diagrams
2. Upgrade and install required packages

sudo apt update
sudo apt upgrade
sudo apt install git i2c-tools libi2c-dev dkms

3. Add i2c-dev to /etc/modules using your favourite editor
4. Edit /boot/firmware/config.txt and uncomment or add the following 2 lines:

dtparam=i2c_arm=on 
dtparam=i2s=on

5. Reboot for changes to take effect
6. Clone the repository and cd into it.

git clone https://github.com/SynAckFin/Echo-Retasker.git

7. Setup various gpios. The privacy LED should turn off.

sh gpiosetup

8. Build and test the LED ring app.

cd ledring
make
./ledring -h
./ledring test
cd ..

9. Build and install the ADC driver

cd driver
sudo make install
sudo dtoverlay echo-2mic

10. Configure the audio (only needs to be done once)

alsactl --no-ucm -f asound.conf restore

11. Record 30 seconds of audio to test microphones

arecord -D plughw:CARD=echo2micvoiceca,DEV=0 -r 16000 -c 2 -f S16_LE -t wav -d 30 test.wav