Thread Switch

Table of Contents

• Project Management
• Hardware
• Border Router
• Battery Life
• Latency

Project Management

Init

mkdir project-nrf-thread-switch
cd project-nrf-thread-switch
docker run --rm -u $(id -u):$(id -g) -v $(pwd):/new -w /new zephyrprojectrtos/ci \
        bash -c "west init -m https://github.com/fgervais/project-nrf-thread-switch.git . && west update"

Add Thread network key

Add secret.conf in the app folder with content like this which matches your network key:

CONFIG_OPENTHREAD_NETWORKKEY="00:11:22:33:44:55:66:77:88:99:aa:bb:cc:dd:ee:ff"

Docker environment

Build

cd application
docker compose run --rm nrf west build -b [email protected] -s app

menuconfig

cd application
docker compose run --rm nrf west build -b [email protected] -s app -t menuconfig

Clean

cd application
rm -rf build/

Update

cd application
docker compose run --rm nrf west update

Flash

nrfutil

cd application
docker compose run --rm nrf nrfutil pkg generate \
        --hw-version 52 --sd-req=0x00 \
        --application build/zephyr/zephyr.hex \
        --application-version 1 first.zip

docker compose -f docker-compose.yml -f docker-compose.device.yml run nrf \
        nrfutil dfu usb-serial -pkg first.zip -p /dev/ttyACM0

pyocd

cd application
pyocd flash -e sector -t nrf52840 -f 4000000 build/zephyr/zephyr.hex

Hardware

• https://github.com/fgervais/project-MS88SF3-breakout
• https://github.com/fgervais/project-nrf-thread-switch_hardware/tree/master/cardboard-enclosure

Border Router

Setup the RCP firmware on an nRF52840 Dongle

git clone --recursive https://github.com/openthread/ot-nrf528xx.git
cd ot-nrf528xx

wget https://developer.arm.com/-/media/Files/downloads/gnu-rm/9-2020q2/gcc-arm-none-eabi-9-2020-q2-update-"$(arch)"-linux.tar.bz2
tar xf gcc-arm-none-eabi-9-2020-q2-update-x86_64-linux.tar.bz2

docker run --rm -u $(id -u):$(id -g) -v $(pwd):/workdir/project nordicplayground/nrfconnect-sdk:v2.0-branch \
        bash -c 'PATH=$PATH:/workdir/project/gcc-arm-none-eabi-9-2020-q2-update/bin ./script/build nrf52840 USB_trans -DOT_BOOTLOADER=USB'
docker run --rm -u $(id -u):$(id -g) -v $(pwd):/workdir/project nordicplayground/nrfconnect-sdk:v2.0-branch \
        bash -c 'PATH=$PATH:/workdir/project/gcc-arm-none-eabi-9-2020-q2-update/bin arm-none-eabi-objcopy -O ihex build/bin/ot-rcp build/bin/ot-rcp.hex'
docker run --rm -u $(id -u):$(id -g) -v $(pwd):/workdir/project nordicplayground/nrfconnect-sdk:v2.0-branch \
        nrfutil pkg generate --hw-version 52 --sd-req=0x00 --application build/bin/ot-rcp.hex --application-version 1 build/bin/ot-rcp.zip
docker run --rm -u $(id -u):$(id -g) -v $(pwd):/workdir/project --group-add 20 --device /dev/ttyACM2 --device /dev/bus/usb nordicplayground/nrfconnect-sdk:v2.0-branch \
        nrfutil dfu usb-serial -pkg build/bin/ot-rcp.zip -p /dev/ttyACM2

Related documentation: https://developer.nordicsemi.com/nRF_Connect_SDK/doc/latest/matter/openthread_rcp_nrf_dongle.html

Start OTBR

sudo modprobe ip6table_filter
docker run --sysctl "net.ipv6.conf.all.disable_ipv6=0 net.ipv4.conf.all.forwarding=1 net.ipv6.conf.all.forwarding=1" -p 8080:80 --volume /dev/ttyACM0:/dev/ttyACM0 --privileged openthread/otbr --radio-url spinel+hdlc+uart:///dev/ttyACM0 --nat64-prefix "fd00:64::/96"

We use --nat64-prefix "fd00:64::/96" so the nat64 will also forward to private ipv4 addresses.

With the default prefix those forwards are prohibited by RFC 6052.

Battery Life

Power consumption (Internal DC/DC)

Idle

Average: 2.53µA

The code wakes up every 10 minutes to feed watchdogs and ping the MQTT server.

Button press

Each press: 291µC

CR2032 expected life (Internal DC/DC)

Based on commit 86a8f0d48d40cb53c8402efef65e8f0e1f45dbd9

Energizer CR2032 = $810 \, C$

Idle all the time

$$\frac{810 \, C}{2.53 \times 10^-6 \, \frac{C}{s}} = 320.158 \times 10^6 \, s$$ $$320.158 \times 10^6 \, seconds \times \frac{1 \, minute}{60 \, second} \times \frac{1 \, hour}{60 \, minute} \times \frac{1 \, day}{24 \, hour} \times \frac{1 \, year}{365.25 \, days} = 10.15 \, years$$

50 presses per day

Idle consumption per day:

$$2.53 \times 10^-6 \, \frac{C}{s} \times (60 \times 60 \times 24) = 218.59 \times 10^-3 \frac{C}{day}$$

Press consumption per day:

$$291 \times 10^-6 \, C \times 50 = 14.55 \times 10^-3 \, C$$

Total per day:

$$218.59 \times 10^-3 \frac{C}{day} + 14.55 \times 10^-3 \, \frac{C}{day} = 233.14 \times 10^-3 \, \frac{C}{day}$$

Runtime:

$$810 \, C \div 233.14 \times 10^-3 \, \frac{C}{day} = 3474 \, days = 9.51 \, years$$

Note: We did not substract the press time from the idle time. It will affect negatively the calculated expected runtime but it should be negligible.

Power consumption (Internal LDO)

This would be the consumption for boards where the inductor is not populated.

Idle

Average: 3.08µA

The code wakes up every 10 minutes to feed watchdogs and ping the MQTT server.

Button press

Each press: 529µC

CR2032 expected life (Internal LDO)

Based on commit 0b7e4261842cd136ae4fb1d94227af606ecbea2d

Energizer CR2032 = $810 \, C$

Idle all the time

$$\frac{810 \, C}{3.08 \times 10^-6 \, \frac{C}{s}} = 262.987 \times 10^6 \, s$$ $$262.987 \times 10^6 \, seconds \times \frac{1 \, minute}{60 \, second} \times \frac{1 \, hour}{60 \, minute} \times \frac{1 \, day}{24 \, hour} \times \frac{1 \, year}{365.25 \, days} = 8.33 \, years$$

50 presses per day

Idle consumption per day:

$$3.08 \times 10^-6 \, \frac{C}{s} \times (60 \times 60 \times 24) = 266.11 \times 10^-3 \frac{C}{day}$$

Press consumption per day:

$$529 \times 10^-6 \, C \times 50 = 26.45 \times 10^-3 \, C$$

Total per day:

$$266.11 \times 10^-3 \frac{C}{day} + 26.45 \times 10^-3 \, \frac{C}{day} = 292.56 \times 10^-3 \, \frac{C}{day}$$

Runtime:

$$810 \, C \div 292.56 \times 10^-3 \, \frac{C}{day} = 2768 \, days = 7.58 \, years$$

Note: We did not substract the press time from the idle time. It will affect negatively the calculated expected runtime but it should be negligible.

Latency

The latency has been tested on the following configuration:

The total latency from electrical button press to light getting out from the bulb is about 85ms.

Demo video

https://youtu.be/jIQvGgGMjlc?si=NDuA6ThBVkoR1B08

Button press to MQTT publish ACK reception

This is the time from the button press event of the Zephyr subsystem to receiving the Publish ACK from the MQTT server.

Those logs are enabled from those settings:

CONFIG_INPUT_LOG_LEVEL_DBG=y
CONFIG_NET_TCP_LOG_LEVEL_DBG=y

[00:22:36.410,217] <dbg> zephyr_gpio_keys: gpio_keys_change_deferred: gpio_change_deferred gpio-keys0 pin_state=0, new_pressed=1, key_index=0
[00:22:36.410,247] <dbg> zephyr_gpio_keys: gpio_keys_change_deferred: Report event gpio-keys0 1, code=10
[00:22:36.410,308] <inf> main: GPIO_KEY gpio-keys0 pressed, zephyr_code=10, value=1
[00:22:36.410,369] <inf> mqtt: 📤 action_button/732107abe638a2a4/trigger/button_short_press_button_1/action
[00:22:36.410,400] <inf> mqtt:    └── payload: PRESS
[00:22:36.410,461] <inf> openthread: 👋 request low latency (mqtt_publish)
[00:22:36.410,491] <inf> openthread: ⏰ events: 00000001
[00:22:36.410,491] <inf> openthread:    └── ⏩ start low latency
[00:22:36.410,827] <dbg> net_tcp: tcp_window_full: (input): conn: 0x2001c8b8 window_full=0
[00:22:36.410,858] <dbg> net_tcp: net_tcp_queue_data: (input): conn: 0x2001c8b8 Queued 84 bytes (total 84)
[00:22:36.410,888] <dbg> net_tcp: tcp_unsent_len: (input): unsent_len=84
[00:22:36.411,285] <dbg> net_tcp: tcp_out_ext: (input): ACK,PSH Seq=2990292615 Ack=967402262 Len=84
[00:22:36.411,529] <dbg> net_tcp: tcp_send_process_no_lock: (input): ACK,PSH Seq=2990292615 Ack=967402262 Len=84 
[00:22:36.411,773] <dbg> net_tcp: tcp_send: (input): ACK,PSH Seq=2990292615 Ack=967402262 Len=84
[00:22:36.412,658] <dbg> net_tcp: tcp_send_data: (input): conn: 0x2001c8b8 total=84, unacked_len=84, send_win=2730, mss=1220
[00:22:36.412,689] <dbg> net_tcp: tcp_send_data: (input): conn: 0x2001c8b8 send_data_timer=0, send_data_retries=0
[00:22:36.412,719] <dbg> net_tcp: tcp_unsent_len: (input): unsent_len=0
[00:22:36.412,872] <dbg> net_tcp: tcp_window_full: (input): conn: 0x2001c8b8 window_full=0
[00:22:36.442,535] <dbg> net_tcp: tcp_in: (rx_q[0]): ACK,PSH Seq=967402262 Ack=2990292699 Len=4 [ESTABLISHED Seq=2990292615 Ack=967402262]

In this specific sample, it is about 32ms.

In my experience, it is quite stable around that time.

Server point of view

The server is composed of home-assistant and eclipse-mosquitto containers.

MQTT publish message reception to Wiz light ON message

This is the time from when the server receives the publish message notifying a button press to when the Wiz integration of Home Assistant gets the turn ON request out.

About 2ms.

MQTT publish message reception to Wiz light ON confirmation

This is the time from when the server receives the publish message notifying a button press to when the server receives the confirmation from the bulb that it turned ON.

About 77ms.