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Frequent Visitor

Using PowerAutomate to talk to Tuya devices

I am busy with an energy saving applications. In this I need to simply switch power to my geyser to make sure it is switched on when the sun is shining (This is connected to a set of rules, all defined in PowerApps).


I have a Tuya compatible switch, user id and secret code. I studied the API and can execute the switching function both in the Tuya platform and got it working in Postman. There is an amount of pre-processing that needs to happen to get a token (Use usercode, secret, time, etc in a Shifting algorithm to get a token valid for 2 hours, that can be refreshed). I tried powerapps custom connector development (it seems similar to OAuth2.0, but I cannot find a place to add the code (this is defined in Postman as a pre-request script). All of this written in JavaScript.   


Is there a non-obvious place to add the JavaScript? Is there a different way to go aboy


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Multi Super User
Multi Super User

Custom connectors have a place to add code but it needs to be in C#

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Multi Super User
Multi Super User

Custom connectors have a place to add code but it needs to be in C#

Frequent Visitor

Thanks, I am actually pursuing to build custom connector to calculate the token alone, my c# skills just very low. I am just worried that I am over-complicating things.


There is an option to import a postman script. I imported a working postman script through the import method. 


It created all the flows in the custom connectors, but uses variables setup as pm.environment variables 

like below:



It misses a set of functions used to calculate the variables.




Below Postman Pre-request Java script for info:

I guess I could try and translate this to c#, but this might deceive the object.

(function () {
pm.environment.set("variable_key", "variable_value");
    var timestamp = getTime();

    const clientId = pm.environment.get("client_id");
    const secret = pm.environment.get("secret");

    var accessToken = "";
        accessToken = pm.environment.get("easy_access_token")

    const httpMethod = pm.request.method.toUpperCase();
    const query = pm.request.url.query;
    const mode = pm.request.body.mode;
    const headers = pm.request.headers;
    // sha256
    var signMap = stringToSign(query, mode, httpMethod, secret)
    var urlStr = signMap["url"]
    var signStr = signMap["signUrl"]
    pm.request.url = + urlStr
    var nonce = ""
    if (headers.has("nonce")) {
        var jsonHeaders = JSON.parse(JSON.stringify(headers))
            if (item.key == "nonce" && !item.disabled) {
                nonce = headers.get("nonce")
    var sign = calcSign(clientId, timestamp, nonce, signStr, secret);
    pm.environment.set('easy_sign', sign);

function getTime(){
    var timestamp = new Date().getTime();
    return timestamp;

// Token verification calculation
function calcSign(clientId,timestamp,nonce,signStr,secret){
    var str = clientId +timestamp + nonce + signStr;
    var hash = CryptoJS.HmacSHA256(str, secret);
    var hashInBase64 = hash.toString();
    var signUp = hashInBase64.toUpperCase();
    return signUp;

// // Business verification calculation
// function calcSign(clientId,accessToken,timestamp,nonce,signStr,secret){
//     var str = clientId + accessToken +timestamp + nonce + signStr;
//     var hash = CryptoJS.HmacSHA256(str, secret);
//     var hashInBase64 = hash.toString();
//     var signUp = hashInBase64.toUpperCase();
//     return signUp;
// }

// Generate signature string
function stringToSign(query, mode, method, secret){
    var sha256 = "";
    var url = "";
    var headersStr = ""
    const headers = pm.request.headers;
    var map = {}
    var arr = []
    var bodyStr = ""
        toJsonObj(query, arr, map)
    if (pm.request.body && mode) {
        if (mode != "formdata" && mode != "urlencoded"){
            bodyStr = replacePostmanParams(pm.request.body.toString())
        } else if (mode == "formdata") {
            // Traversing form key value pairs
            toJsonObj(pm.request.body["formdata"], arr, map)
        } else if (mode == "urlencoded") {
            // Traversing form key value pairs
            toJsonObj(pm.request.body["urlencoded"], arr, map)
    sha256 = CryptoJS.SHA256(bodyStr)
    arr = arr.sort()
            url += item + "=" + map[item] + "&"
    if (url.length > 0 ) {
        url = url.substring(0, url.length-1)
        url = "/" + pm.request.url.path.join("/") + "?" + url
    } else {
        url = "/" + pm.request.url.path.join("/")
    if (headers.has("Signature-Headers") && headers.get("Signature-Headers")) {
        var jsonHeaders = JSON.parse(JSON.stringify(headers))
        var signHeaderStr = headers.get("Signature-Headers")
        const signHeaderKeys = signHeaderStr.split(":")
            var val = ""
            if (isSelected(jsonHeaders,item) && headers.get(item)) {
                val = headers.get(item)
            headersStr += item + ":" + val + "\n"
    var map = {}

    url = replacePostmanUrl(url)    
    map["signUrl"] = method + "\n" + sha256 + "\n" + headersStr + "\n" + url
    map["url"] = url
    return map

function isSelected(jsonHeaders,key){
    var result = true;
        if (item.key == key && item.disabled) {
            result = false
    return result

function replacePostmanParams(str){
        const key = str.substring(str.indexOf("{{")+2,str.indexOf("}}"))
        var value = pm.environment.get(key)
        if(!value) value=""
        str = str.replace("{{"+key+"}}", value)
    return str

function replacePostmanUrl(str){
        const key = str.substring(str.indexOf("{{")+2,str.indexOf("}}"))
        var value = pm.environment.get(key)
        if(!value) value=""
        str = str.replace("{{"+key+"}}", value)

        const tempStr = str.substring(str.indexOf(":")+1,str.length);
        var key = "";
            key = tempStr.substring(0,tempStr.indexOf("/"))
        }else if(tempStr.indexOf("?")!=-1){
            key = tempStr.substring(0,tempStr.indexOf("?"))
        }else {
            key = tempStr.substring(0,tempStr.length)
        var value = pm.request.url.variables.get(key)
        if(!value) value=""
        str = str.replace(":"+key, value)
    return str

function toJsonObj(params, arr, map){
    var jsonBodyStr = JSON.stringify(params)
    var jsonBody = JSON.parse(jsonBodyStr)
            map[item.key] = item.value




I implemented a combination of Powerautomate and Custom Connectors if anybody is interested.


I created the following:

Custom Connector 1. This only has C# code which I translated from jScript in Postman. This calculates the signstring to be used for the token call

Flow : Execute Custom connector to get parameters, parse JSON,  and then use this to calculate the token

Custom Connector 2. This takes the token and convert it to a signstring for commands (different for on and off)

Depending on on or off parameter set in input to flows.

Flow : Use parameters retrieved above , Parse JSON to perform a command call for on or off.


I previously built a connector to my inverter and can now do multiple calculations in powerapps to optimize powerusage for my geyser.


Project not complete, but learnt a lot. 

I would be interested in using this for my thermostat and window blinds. (both for temperature and insolation control).  I guess I have to figure out the JSON for the control calls?


Frequent Visitor

I think the first to determine is the API for the manufacturer of your devices. In my case, Tuya provided this platform. Also consider IFFFTT as a platform. Next step is to apply for the API username and password and getting a manual for the calls to be performed. Once there, just a question of figuring out the steps in your flow.


This could be an interesting control project.


The reason why I had to include the coding part was  because Tuya has a very elaborate authentication mechanism. Other connectors that I built was much less complicated (eg to my inverter).

Understood. All the devices I mentioned are Tuya based.

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