D1 ThingSpeak Heartbeat

Abstract

A most minimal setup to detect missing heartbeats provoked by an power- or network-outage.

Prerequisites

• Wemos D1 Mini at hand
• ThingSpeak / MATHLAB account exists
• Slack Incomming Webhook Integration exists

ThingSpeak channels

At thingspeak.com/channels create a Channel and note the Channel ID, Write API Key and Read API Key.

MATHLAB Analyses

At thingspeak.com/apps/matlab_analyses create a MATLAB Analysis with name Write 0 to Heartbeat if last Heartbeat too old and content:

try
    [bla,heartbeat] = thingSpeakRead(967121,'ReadKey',"ZHOXUL2C6VMJNJ3U",'NumPoints',1,'Fields',1);

    now = datetime('now','Format','dd-MMM-yyyy HH:mm:ss');

    % write a 0 so React has something to react on
    if minutes(duration(now-heartbeat)) > 3
        thingSpeakWrite(967121,0,'WriteKey',"KO0T51GCEWV76VN3");
    end
catch someException
    fprintf("Failed to send alert: %s\n", someException.message);
end

MATHLAB TimeControl

At thingspeak.com/apps/timecontrols create a New TimeControl with the name Run Heartbeat Evaluation and the following settings:

Field	Value
Frequency	Recurring
Recurrence	Minute
Every	5
Action	MATHLAB Analyses
Code to execute	Write 0 to Heartbeat Casa if last Heartbeat too old

MATHLAB ThingHTTP

At https://thingspeak.com/apps/thinghttp create a New ThingHTTP with the name Slack Event Outage and the following settings:

Field	Value
URL	https://hooks.slack.com/services/TVWG8R3TY/B8X88x5/HCmVtHqsehKy2VKKYQIxQlJnw7
Method	POST
Content Type	application/json
Host	hooks.slack.com
Body	{'text': 'CASA OUTAGE', 'username': 'ThingSpeak'}

At https://thingspeak.com/apps/thinghttp create a New ThingHTTP with the name Slack Event Recover and the following settings:

Field	Value
URL	https://hooks.slack.com/services/TVWG8R3TY/B8X88x5/HCmVtHqsehKy2VKKYQIxQlJnw7
Method	POST
Content Type	application/json
Host	hooks.slack.com
Body	{'text': 'RECOVER', 'username': 'ThingSpeak'}

MATHLAB React

At https://thingspeak.com/apps/reacts create a New React with the name Outage Detect and the following settings:

Field	Value
Condition Type	Numeric
Test Frequency	On data insertion
Channel	{your channel}
Condition	Field 1 (heartbeat) is equal to 0
Action	ThingHTTP :: Slack Event Outage
Run	Only the first time the condition is met

At https://thingspeak.com/apps/reacts create a New React with the name Recover Detect and the following settings:

Field	Value
Condition Type	Numeric
Test Frequency	On data insertion
Channel	{your channel}
Condition	Field 1 (heartbeat) is equal to 1
Action	ThingHTTP :: Slack Event Recover
Run	Only the first time the condition is met

Wemos D1 Mini

Upload the code with your settings (see main.h) to the Wemos D1 Mini.

Setting	Description	Environment Var
wifi_ssid	The Wifi SSID the D1 Mini connects to.	WIFI_SSID
wifi_pass	The password used to connect to Wifi.	WIFI_PASS
thingspeakApiKey	Write API Key for the heartbeat channel.	THINGSPEAK_HEARTBEAT