GSS Mahadevan's Blog: Home Automation

Setup of IoT system

I was using a Raspberry-Pi #B (35$ ARM processor, RPi) for home autoamation running as edge router/server . I have a customized golang server that connects to my IoT sensors and updates to postgres DB (previously I used TICK stack , but I had Influxdb corruption issues, so I switched to postgres DB). All of these apps are hosted in docker-instances inside the RPi. I still use Graphana as front-end GUI (after I added the postgres as datasource to Grapahana).

Disk configuration to separate OS with applications

To safegaurd RPi going to Denial-Of-Service mode due to root disk-starvation, I have used extra USB-stick for customized-Apps, Postgress DB, Graphana and other docker instances. In this way, if any applications (including graphana, postgres, influx, customized apps) fills-up disk , one can still access RPi as RPi's SD-Card is still in good-shape (wrt to disk space).

Telegram-Bot integration

Recently I have added support for Telegram-Bot integration with my RPi , so that I can communicate to my RPi outside my home WiFI network. The integration went well and I can issue commands from Telegram app and handle in RPi (evetually I can reach my sensors).

Telegram-Bot transient error cauing DoS situation

Everything went fine till I switched off my home WiFi network in home. The moment I switched off WiFi network, the third party Telegram-Bot framework started to fills up the USB-Disk (which is shared by docker instances, customized apps,etc) as my customized-app's stdout/stderr are routed to USB-disk (for debugging/post-mortem-analysis). Within 12 hours of night time, 8GB of data is filled up. If this fillup is continued, within another 12 hours all of my docker instances (postgres, graphana and my customized app will have DoS siatuation.

Solution

To mitigate the above DoS situation, I could route the stdout/stderr to /dev/null, but I will lose information in case of critical errors(apart from this error) from third-party-code-bases and any unhandled golang's stack-traces and panic outputs.

For handling all the above tricky situations, I have written small golang application named safeout that consumes stdout/stderr of any number of processes and redirects the output of each stdout/stderr into disk-files with checks on maximum size (with one backup file).

I configured my customized application with above safeout . Now myApp (or any other app in docker instance ) starts redirecting stdout/stderr to disk, they will not fill-up disk (as safeout will ensure maximum disk space limits are honored with one backup copy)

safeout Code is at Safeout

For my home automation projects, I have been doing lots of R&D on various factors like:

Low cost MCU and MCU related board (commercially available)
Low power consumption in deep sleep (may not be the best , but reasonable low current consumption, so that MCU can withstand power outages)

Lots of cheap boards are there. For the time being I have chosen following Arduino boards

Arduino Pro Mini clone for 4.25$ per board with free shipping

Cheap availability of wireless connectivity solutions

Bluetooth 4.0

In coming future, I would be using BLE-Soc chips likeNordic nrf51822 and TI's cc2540 & cc2541 -- as we have cheap assembled boards at various internet shops (like alibaba, dealsextreme, ebay, etc) .These boards typically come for 6 to 12$

Zigbee

I tried initially, but their board's cost is high very high even at above shops and difficult solder because of QFN-soldering, wireless antenna's design, etc.

Proprietary wireless protocol

I found Nordic radio transceiver NRF24L01+ at 2.4GHz spectrum at following site for around 1$ per board

Free compiler, open source libraries & knowledge base in net. If not free some trial based compiler for doing R&D (like cc254x chips).

Arduino fits the bill, but their overall solution costs more than 15 to 20$ before an year back (with my research at that point of time). So I dropped Arduino idea and looking for other solutions. Recently I casually browsed Alibaba site and found that I can get a reasonably powered Ardunio for less than 5$ and wireless connectivity for another 1$. So brought these items and finally started doing first helloworld on this boards.

Here are pictures for this board

This is for connecting this board with typically USB-to-Serial-Dongle(Prolific based) and correpsonding RS232 TTL convertor

This is showing minimal connections needed for powering and burning the program to Arduino. These yellow wires do connect to above USB-RS232-Dongle (RX & TX appropriately)

Board view from top view with an empty board on side

Connections from Arduino Board to RS232

Please ensure that you connect serial port cross-connection like following:

Board-Longer-Side RXI to RS232 TX

Board-Longer-Side TXD to RS232 RX

Arduino IDE Options

Select proper Serial port
Select board as either of these boards. For my both voltages have worked out

'Arduino Prop or Pro Mini (5V, 16MHz) w/ Atmega328'
'Arduino Prop or Pro Mini (3.3 V, 8MHz) w/ Atmega328'

Select Programmer as 'Arduino as ISP'

Actions need to be taken while pressing Upload from IDE

As current setup does not use DTR/RTS on RS232 and only uses RX/TX (from USB to Rs232 converter), we need to press reset button just before the flashing (i.e., when console logs shows lines something like following in verbose-burning-mode-preferences)

Using Port : /dev/ttyUSB0

Using Programmer : arduino

Overriding Baud Rate : 57600

avrdude: Send: 0 [30] [20]

For more details on why we need to press reset button, refer following section Automatic (Software) Reset in given link

Problems/Issues faced

Serial Port not detected in Linux

Run as root, then the Arduino IDE recognizes the Serial port . Select appropriate serial port from output of 'dmesg' command in linux.

Flashing Issues

After selecting the board as 'Arduino Prop or Pro Mini (5V, 16MHz) w/ Atmega328' and correct serial port. After trying to flash image to board has given following error messages.

Binary sketch size: 2,654 bytes (of a 30,720 byte maximum)avrdude: stk500_recv(): programmer is not responding

Now enable the verbose upload option via File -- Preference --'Show verbose output during' = 'burning' .

After this step , I got following messages

Binary sketch size: 2,654 bytes (of a 30,720 byte maximum)

**/arduino-1.0.5/hardware/tools/avrdude -C/opt/arduino-1.0.5/hardware/tools/avrdude.conf -v -v -v -v -patmega328p -carduino -P/dev/ttyUSB0 -b57600 -D -Uflash:w:/tmp/build5308589158935848821.tmp/ASCIITable.cpp.hex:i

avrdude: Version 5.11, compiled on Sep 9 2011 at 16:00:41

System wide configuration file is "**/arduino-1.0.5/hardware/tools/avrdude.conf"

User configuration file is "***/.avrduderc"

User configuration file does not exist or is not a regular file, skipping

Using Port : /dev/ttyUSB0

Using Programmer : arduino

Overriding Baud Rate : 57600

avrdude: Send: 0 [30] [20]

avrdude: ser_recv(): programmer is not responding

avrdude: stk500_recv(): programmer is not responding

avrdude done. Thank you.

Another error which slightly different at end

Using Port : /dev/ttyUSB0

Using Programmer : arduino

Overriding Baud Rate : 57600

avrdude: Send: 0 [30] [20]

avrdude: Recv: . [00]

avrdude: stk500_getsync(): not in sync: resp=0x00

avrdude done. Thank you.

As this not typical USB based driver (which is available in little costlier Arduino boards) and I am using hard coded RS232 wiring, I tried to flash the image by pressing the reset button on the board. This made the flashing to occur successfully. Actually if we reset the board, MCU waits for flashing-data from RX/TX pins few seconds. If no recognized flashing data comes to RX/TX pins, MCU will boot with previous programm that is there in flash. One has to find appropriate time to press reset button -- this timing can be assisted by putting verbose-burning-option.
So successful flash sequence is shown as:

Binary sketch size: 2,654 bytes (of a 30,720 byte maximum)

***/arduino-1.0.5/hardware/tools/avrdude -C***/arduino-1.0.5/hardware/tools/avrdude.conf -v -v -v -v -patmega328p -carduino -P/dev/ttyUSB0 -b57600 -D -Uflash:w:/tmp/build5308589158935848821.tmp/ASCIITable.cpp.hex:i

avrdude: Version 5.11, compiled on Sep 9 2011 at 16:00:41

System wide configuration file is "***/arduino-1.0.5/hardware/tools/avrdude.conf"

User configuration file is "***/.avrduderc"

User configuration file does not exist or is not a regular file, skipping

Using Port : /dev/ttyUSB0

Using Programmer : arduino

Overriding Baud Rate : 57600

avrdude: Send: 0 [30] [20]

avrdude: Recv: . [14]

avrdude: Recv: . [10]

AVR Part : ATMEGA328P

Chip Erase delay : 9000 us

PAGEL : PD7

BS2 : PC2

RESET disposition : dedicated

RETRY pulse : SCK

serial program mode : yes

parallel program mode : yes

Timeout : 200

StabDelay : 100

CmdexeDelay : 25

SyncLoops : 32

ByteDelay : 0

PollIndex : 3

PollValue : 0x53

Memory Detail :

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