Project to control IKEA hydroponics Krydda/ Växer

I'm starting a new project with the brand new indoor gardening system from IKEA which is named "Krydda"/ "Växer".

This is a picture of the initial seed:

Initial seed day 0

Planned items are to control and optimize growth with a microcontroller/ embedded system and sensors (light, humidity, temperature, CO2, water level etc.) utilizing automated lighting and water refill with the new IKEA Krydda/ Växer system.

You can follow the project here and at my github repo

Raspberry Pi 3 "Echo"

Building an Amazon Echo similar device out of a Raspberry Pi 3

I recently worked as an electronics hardware developer on a new smarthome system which is designed to have speech recognition as a way of controlling devices.

Over the course of researching soft- and hardware for this purpose while in Silicon Valley I also tested and reverse engineered the "Amazon Echo" - an electronically very well designed device and a huge success for one of the in-house manufactured devices from the electronic commerce and cloud computing company.

The latter also lays the groundwork for Amazon Echo and the speech recognition called "Alexa" utilized in the round tower like gadget. With a price tag of $180 and - more important - not yet available to customers outside the US I was quite happy back in Europe to see a github repo to allow implementing an Amazon Echo similiar device and especially speech recognition on cheap hardware like a Raspberry Pi.

I bought the quite new Raspberry Pi 3 - even if the github repo uses a Pi 2 - expecting some minor issues, what turned out to be true. A big help was to browse the "issues" related to the repo.

In short I avoided to install a new JDK because it already comes with new Raspian Jessie image. I put on the newest version of Node.js, used the WiFi which is onboard with the RasPi3 and tested different microphones because the one suggested on the github repo has some bad reviews. That's basically all I deviated from the original installation instructions, which worked out very well.

After only two hours or so everything was set up without problems. In the video below and for the first tests I used a webcam with an integrated microphone, a Logitech QuickCam Orbit AF, which I had lying around while the dedicated USB microphone was ordered but had not arrived.

Identifying the microphone chipset

The problems began when I got the new USB microphone, a "Lerox USB microphone" ordered - of cause - from Amazon. In the beginning I had barely no success getting "Alexa" recognizing my commands. I had pulsing sounds (which I hadn't before) and the speech recognition stopped before I could even tell the whole command. The microphone identifies as a "C-Media Electronics device" with a CM108-chipset.

Three efforts led me to success:

Microphone configuration with "alsamixer"

1. I adjusted the recording settings of the microphone with "alsamixer". It turned out to be a good setting (at least for the microphone used) when it is set to the highest "green" level available.

2. I changed the USB power supply for the Raspberry Pi 3. This is where the klicking sound while recording the commands came from. Might be more a bad design of the microphone than of the power supply, as I used a high quality PSU first.

Editing settings for the microphone

3. This might be the most important setting fiddling with microphone problems: I adjusted the values in the java source code (../samples/javaclient/src/main/java/com/amazon/alexa/avs/ASVApp.java) for "ENDPOINT_THRESHOLD" (minimum audio level threshold under which is considered silence) and "ENDPOINT_SECONDS" (amount of silence time before endpointing). Default was 5 respectively 2 which I changed to 7 and 4. After a "mvn install" to do a new build and the call "mvn exec:exec" it now almost works like the original Amazon Echo.

Audio device settings

4. You might have to set your microphone as default input source. You can do this by choosing "Menu -> Settings -> Audio Device Settings" selecting your soundcard (microphone), add elements and make the microphone the default. This is where you can also set the gain or any additional elements like auto gain control (AGC) when provided by the soundcard/ microphone. As far as I understand choosing and setting the microphone with "alsamixer" does the same but I'm not sure about it.

The next thing I will implement is the invocation with a spoken command like the Amazon Echo - where you can choose between "Alexa" and "Amazon". As far as I could reverse engineer it Amazon solves this with a bunch of Texas Instruments TLV320ADC3101 92dB SNR Low-Power Stereo ADCs, which have an integrated miniDSP and I guess this is where they put the algorithms (aka "magic") for recognizing the invocation command while after this streaming the rest to their cloud servers. You find a lot of technical details of the Amazon Echo in this awesome ifixit Amazon Echo teardown .

EDIT 4-10-2016: Added instructions of Elton "Eddie" Hartmans fork to the installation on my Raspberry Pi 3 and it's now possible to start voice commands either by clicking the button on the JAVA-GUI or by pressing a switch connected to the GPIOs of the Raspberry Pi.

EDIT 4-25-2016: If you want to use bluetooth speakers follow this awesome tutorial from David Roberts. Unfortunately I wasn't able to connect my microphone which is embedded in my bluetooth speaker BoomStar BT NFC X yet.

Level-Shifter for XBee & Raspberry Pi

Some projects have mixed supply voltages (e.g. 5 Volt and 3.3 Volt) and sometimes integrated circuits don't work with those unequal signal levels - or worse get damaged by the higher level supply signals.

Level shifter pcb

In case of the XBee which is driven by 3.3 Volt up to now I added a simple resistor divider to get the signals down to the lower supply level (see this older post ). But even if you feed the XBee without translating the different supply levels, I never got any problems (but I wouldn't recommend).

It might look slightly different with the Raspberry Pi, so to be on the safe side I built a simple 2-bit bidirectional voltage-level translator circuit for the alleged thin-skinned RasPi. You just need four 10k resistors, two BSS138 (N-Channel Logic Level Enhancement Mode Field Effect Transistor) and two four-pin headers.

I etched the board by myself but if you want to take the short way, there are already breakout boards and ICs available (e.g. Sparkfun Logic Level Converter, TXS0102 from Texas Instruments or ADuM1250/ ADuM1251 from Analog Devices).

Anyway I wanted to do some practice with my favourite pcb layout software Eagle and designed this simple pcb.

How does the level shifting work? If nothing happens on the bus (in this special case on the I2C-bus, thats what the pcb is labled for, but it also works with RX/ TX or any other 2-bit bidirectional digital purposes) all signals are pulled high by the 10k resistors. If either side goes low, the N-Channel MOSFET steps in and also pulls the signal line low, either because it turns on (low level side) or passes through the body diode (high level side).

Raspberry Pi and XBee

XBee perfboard hooked up to the Raspberry Pi

One nice gadget to play with is the quite new Raspberry Pi. I added a XBee (Coordinator AT) to the RasPi and sent some serial data to an Arduino UNO (and back) with a XBee attached (Router AT) via serial terminal (minicom) and Python.

The RasPi is running on Debian wheezy and the perfboard is connected via two row header sockets to the GPIO pins.


The 3.3V for the XBee is directly coming from Pin 1 of the GPIO-Header (GND from Pin 6), DOUT is connected to Pin 10 (GPIO RXD) and DIN to Pin 8 (GPIO TXD). I didn't test it with a XBee Pro attached, this will certainly draw too much current from the RasPi. The 3.3V supply only delivers 50mA as per this wiki . This is fine with the normal XBee which has 40mA max. current demand as per datasheet. If you need more current (XBee PRO needs 295mA@3.3V when transmitting with maximum output power) you could use the 5V power source with a subsequent voltage regulator as mentioned in the blog entries before. Be careful to use a voltage regulator with enough capabilities to deliver ample current.

Still enough legroom for the Raspberry Pi

One big advantage beside being wireless is that there is no level converter needed as the signals are 3.3V TTL to and from the Raspberry Pi.

To get the whole thing working you have to modify some settings in Debian wheezy. There is a nice walkthrough in this blog.

If you want to communicate via Python you have to get pyserial (sudo apt-get install python-serial or sudo apt-get install python3-serial for Python3). Example code for Python2 to send a value to the Arduino would look like this:

import serial
xbee=serial.Serial(port='/dev/ttyAMA0',baudrate='9600')
xbee.write('8')


For Python3 you would have to change the last line to:

xbee.write(b'8')


to send as a String.

On the Arduino side you could read the incoming data with Serial.read().

Connecting the whole thing together gives a huge amount of opportunities for future projects as one can use the combined cpu power/ linux system/ graphic abilities of the Raspberry Pi and the microcotroller skills and shields of the Arduinos - everything wirelessly connected in a mesh network.