Using a serial port with Home Assistant to issue ASCII commands.

Forums › Gadgets, robotics, home automation, electronics (including wearables) › Using a serial port with Home Assistant to issue ASCII commands.

fearandloathing

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#270142 25-Apr-2020 11:25

I have all the necessary hardware and can operate the blinds using 'screen' on a raspberry pi via a USB RS485 Cable connected to the blind WiFi bridge.

To connect to the bridge

screen /dev/ttyUSB0 9600

Issue Open Command
!123D001o;
Issue Close Command
!123D001c;

What is the best way to send these commands from Home Assistant, ideally I would like to create a switch in Home Assistant to operate the blinds, with an Open and a Close toggle.

What is the best way to implement this?

richms

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#2471088 25-Apr-2020 14:44

Node red can talk to serial ports. I followed along an example and had it working but then changed to using an esp8266 instead so I got electrical disconnection from the device.

Richard rich.ms

phrozenpenguin

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#2471265 25-Apr-2020 19:43

I've done this in Node Red, albeit for a different device. Node Red is easy to setup using Home Assistant Add-Ons.

What blinds are you using?

fearandloathing

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#2471296 25-Apr-2020 20:38

A couple of different brands, some honeycomb blinds (Kinetics) and a roller blind (ABC Blinds) ultimately both are dooya motors. Both use the DD7002B wif-fi bridge

I've made progress, I can operate the blinds now from the command line.

( stty raw speed 9600 >&2; echo -ne '!123D001o;' ) >/dev/ttyUSB0 <&1

Although the following switch does not work

switch:
platform: command_line
switches:
nw_dining_blind:
command_on: "( stty raw speed 9600 >&2; echo -ne '!123D001o;' ) >/dev/ttyUSB0 <&1"
command_off: "( stty raw speed 9600 >&2; echo -ne '!123D001c;' ) >/dev/ttyUSB0 <&1"
friendly_name: North West Dining Blind

I don't know if it's character escaping or if I need to run it as a script.

fe31nz

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#2471332 25-Apr-2020 23:22

fearandloathing:

A couple of different brands, some honeycomb blinds (Kinetics) and a roller blind (ABC Blinds) ultimately both are dooya motors. Both use the DD7002B wif-fi bridge

I've made progress, I can operate the blinds now from the command line.

( stty raw speed 9600 >&2; echo -ne '!123D001o;' ) >/dev/ttyUSB0 <&1

Although the following switch does not work

switch:
platform: command_line
switches:
nw_dining_blind:
command_on: "( stty raw speed 9600 >&2; echo -ne '!123D001o;' ) >/dev/ttyUSB0 <&1"
command_off: "( stty raw speed 9600 >&2; echo -ne '!123D001c;' ) >/dev/ttyUSB0 <&1"
friendly_name: North West Dining Blind

I don't know if it's character escaping or if I need to run it as a script.

My guess would be that you have to execute a program to run the script line. So try adding "/bin/bash -c " at the front.

fearandloathing

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#2471571 26-Apr-2020 13:12

fe31nz:

My guess would be that you have to execute a program to run the script line. So try adding "/bin/bash -c " at the front.

Give that person a beer

Solution

switch:
platform: command_line
switches:
blind_dining_nw:
command_on: '/bin/bash -c "( stty raw speed 9600 >&2; echo -ne ''!123D001o;'' ) >/dev/ttyUSB0 <&1"'
command_off: '/bin/bash -c "( stty raw speed 9600 >&2; echo -ne ''!123D001c;'' ) >/dev/ttyUSB0 <&1"'
friendly_name: Blind Dining North West

That is the whole line wrapped in: '

' escaped around the !123D001o;

and the command line pushed to bash wrapped in "

fe31nz

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#2471776 26-Apr-2020 22:50

And now that it works with bash, if you want it to run slightly faster and with lower overheads, you might like to see if it will also work with /bin/sh.

New World

Shop on-line at New World now for your groceries (affiliate link).

fearandloathing

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#2471777 26-Apr-2020 22:56

Is it worth it when the response is instant?

fe31nz

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#2472466 27-Apr-2020 23:48

Bash is a big powerful shell with a massive feature set. It is OK to use it for this sort of thing but if sh will work, it is better to use sh as bash is way overkill for the job. If you have RAM and processor to waste and bash is not being used very often, you probably will not notice any difference. If you use bash like this for something that happens say every second, then you will likely have problems. Here are the sizes of bash and sh (dash) in Ubuntu 18.04:

root@mypvr:~# ll /bin/bash
-rwxr-xr-x 1 root root 1113504 Jun 7 2019 /bin/bash*
root@mypvr:~# ll /bin/sh
lrwxrwxrwx 1 root root 4 Oct 6 2018 /bin/sh -> dash*
root@mypvr:~# ll /bin/dash
-rwxr-xr-x 1 root root 121432 Jan 25 2018 /bin/dash*

So sh (dash in Ubuntu) is 10.9% of the size of bash!

The normal thing to do with command lines like this is to try them with bash, and see if they work. You do this because what you are trying to do may not be possible in sh as it may lack a necessary feature, and you want to initially just get them to work, rather than bothering about what features they need that may not be in sh. Then try again with the restricted feature set of sh. If they work in sh, then use sh. If not, then you may need to rewrite the command to do things using sh only features, or you may decide that bash is fine and just keep using bash.