# Can't read Photon firmware variable from iPhone app (with IOS Cloud SDK) **URL:** \ **Category:** Troubleshooting\ **Created:** [August 20, 2016, 1:57am UTC](https://community.particle.io/t/cant-read-photon-firmware-variable-from-iphone-app-with-ios-cloud-sdk/25245 "2016-08-20T01:57:57Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![douglaskbell](https://avatars.discourse-cdn.com/v4/letter/d/85e7bf/32.png) [@douglaskbell](https://community.particle.io/u/douglaskbell)\ **Post date:** [August 20, 2016, 1:57am UTC](https://community.particle.io/t/cant-read-photon-firmware-variable-from-iphone-app-with-ios-cloud-sdk/25245/1 "2016-08-20T01:57:57Z")
Photon firmware has double variable. I can read it from CLI particle get OK. But from example app of IOS Clos SDK, modified for my variable, nothing seems to happen when I call [myPhoton getVariable … …the ‘completion:’ doesn’t seem to fire. I run on iPhone6+, and do the example app’s “Login” ok and then “Test sequence”. Here’s the FW code and the iOS code: IOS… ```nohighlight printf("\n reading a variable" ); [myPhoton getVariable:@"button_press" completion:^(id result, NSError *error) { if (!error) { NSNumber* button_press = (NSNumber* )result; NSLog(@"button_press is #%f ",button_press.doubleValue); } else { NSLog(@"Failed reading button_press from Photon device"); } }]; ``` FIRMWARE… ```cpp #include "InternetButton/InternetButton.h" /* How about we make this interactive? */ InternetButton b = InternetButton(); double button_press = 0; // none void setup() { // Tell b to get everything ready to go // Use b.begin(1); if you have the original SparkButton, which does not have a buzzer or a plastic enclosure // to use, just add a '1' between the parentheses in the code below. b.begin(); b.setBrightness(50); Serial.begin(9600); Serial.println("Hello World! 2016-08-19a"); } void loop(){ // When you click the second button (at the 3 o'clock position) let's turn that LED on if(b.buttonOn(1)) { button_press = 1; Particle.variable( "button_press", button_press ); b.ledOn(1, 255, 0, 0); b.ledOn(11, 255, 0, 0); Serial.println("button_press = 1"); } else if(b.buttonOn( 2 )) { button_press = 2; Particle.variable( "button_press", button_press ); b.ledOn(2, 0, 255, 0); b.ledOn(3, 0, 255, 0); b.ledOn(4, 0, 255, 0); Serial.println("button_press = 2"); } else if(b.buttonOn(3)) { button_press = 3; Particle.variable( "button_press", button_press ); b.ledOn(5, 0, 0, 255); b.ledOn(6, 0, 0, 255); b.ledOn(7, 0, 0, 255); Serial.println("button_press = 3"); } else if(b.buttonOn( 4 )) { button_press = 4; Particle.variable( "button_press", button_press ); b.ledOn(8, 255, 255, 0); b.ledOn(9, 255, 255, 0); b.ledOn(10, 255, 255, 0); Serial.println("button_press = 4"); } // And if the button's not on, then the LED should be off else { button_press = 0; Particle.variable( "button_press", button_press ); b.ledOff(1); b.ledOff(2); b.ledOff(3); b.ledOff(4); b.ledOff(5); b.ledOff(6); b.ledOff(7); b.ledOff(8); b.ledOff(9); b.ledOff(10); b.ledOff(11); } /* Much like the LEDs, there are also functions to check if all the buttons are on- b.allButtonsOn() or if all the buttons are off- b.allButtonsOff() */ } ``` ---
**Author:** ![Ric](https://sea2.discourse-cdn.com/flex026/user_avatar/community.particle.io/ric/32/514_2.png) [@Ric](https://community.particle.io/u/Ric)\ **Post date:** [August 20, 2016, 5:20am UTC](https://community.particle.io/t/cant-read-photon-firmware-variable-from-iphone-app-with-ios-cloud-sdk/25245/2 "2016-08-20T05:20:09Z")
> [@douglaskbell](#): > > nothing seems to happen when I call [myPhoton getVariable ... What exactly does happen? Anything? Since you said that it seems like the completion code isn't running, I assume that your NSLogs aren't printing out. Have you verified that **myPhoton** is not nil? ---
**Author:** ![douglaskbell](https://avatars.discourse-cdn.com/v4/letter/d/85e7bf/32.png) [@douglaskbell](https://community.particle.io/u/douglaskbell)\ **Post date:** [August 20, 2016, 6:54am UTC](https://community.particle.io/t/cant-read-photon-firmware-variable-from-iphone-app-with-ios-cloud-sdk/25245/3 "2016-08-20T06:54:17Z")
Is there a [build.particle.io](http://build.particle.io) library for Photon firmware that matches (works with) the example app in the IOS Cloud SDK? I’m having trouble getting the IOS Cloud SDK to read a variable in my app on my Internet Button Photon. ---
**Author:** ![ScruffR](https://sea2.discourse-cdn.com/flex026/user_avatar/community.particle.io/scruffr/32/6952_2.png) [@ScruffR](https://community.particle.io/u/ScruffR)\ **Post date:** [August 20, 2016, 7:55am UTC](https://community.particle.io/t/cant-read-photon-firmware-variable-from-iphone-app-with-ios-cloud-sdk/25245/4 "2016-08-20T07:55:28Z")
Sorry that I have to remind you if the docs as well. The way you are using `Particle.variable()` is not how you do it. `Particle.variable()` is only called **_once_** in `setup()` to _expose_ a global variable to the cloud and is **_not_** used to push the value of the variable to the cloud. ---
**Author:** ![douglaskbell](https://avatars.discourse-cdn.com/v4/letter/d/85e7bf/32.png) [@douglaskbell](https://community.particle.io/u/douglaskbell)\ **Post date:** [August 20, 2016, 12:37pm UTC](https://community.particle.io/t/cant-read-photon-firmware-variable-from-iphone-app-with-ios-cloud-sdk/25245/5 "2016-08-20T12:37:08Z")
Ric: After calling getDevices, myPhoton = 0, so getVariables fails. However, according to my logs, getDevices doesn’t seem to run until after testButton() returns. What causes that?? I have made no changes to the example app, other than my login info. ScruffR: Correction made; Particle.variable() now only called once, in setup. Code and output follow… ```nohighlight - (IBAction)testButton:(id)sender { // logging in printf("\n >>>>>> %s...", __FUNCTION__ ); /////////////////////// C O N N E C T W I T H C L O U D ////////////////////// printf("\n loginWithUser" ); [[SparkCloud sharedInstance] loginWithUser:TEST_USER password:TEST_PASS completion:^(NSError *error) { printf("\n loginWithUser" ); if (!error) NSLog(@"Logged in to cloud"); else NSLog(@"Wrong credentials or no internet connectivity, please try again"); }]; // get specific device by name: __block SparkDevice *myPhoton; ///////////////////// D E T E R M I N E O N L I N E D E V I C E S ///////////////////// printf("\n get specific device by name:\n" ); [[SparkCloud sharedInstance] getDevices:^(NSArray *sparkDevices, NSError *error) { printf("\n get specific device by name:\n" ); NSLog(@"%@",sparkDevices.description); // print all devices claimed to user // search for a specific device by name for (SparkDevice *device in sparkDevices) { if ([device.name isEqualToString:@"IB_A"]) // one of my Internet Button Photon's { myPhoton = device; NSLog(@"\n device.name %@ FOUND myPhoton=%x \n", device.name, myPhoton ); } else { NSLog(@"\n device.name %@ NOT FOUND \n", device.name ); } } }]; //////////////////////// R E A D D E V I C E B U T T O N /////////////////////// // reading a variable printf("\n reading a variable" ); [myPhoton getVariable:@"button_press" completion:^(id result, NSError *error) { printf("\n reading a variable" ); if (!error) { NSNumber* button_press = (NSNumber* )result; NSLog(@"button_press is #%f ",button_press.doubleValue); } else { NSLog(@"Failed reading button_press from Photon device"); } }]; // logout [[SparkCloud sharedInstance] logout]; printf("\n <<<<<< %s done.\n\n", __FUNCTION__ ); return; ``` =========================================================== OUTPUT: ```nohighlight ">>>>>>" -[SparkViewController testButton:]... loginWithUser get specific device by name: reading a variable "<<<<<<" -[SparkViewController testButton:] done. loginWithUser2016-08-20 06:15:33.257 AudMan1 x2[2710:942837] Logged in to cloud get specific device by name: 2016-08-20 06:15:33.740 AudMan1 x2[2710:942837] ( "", "" ) 2016-08-20 06:15:33.740 AudMan1 x2[2710:942837] device.name IB-B NOT FOUND 2016-08-20 06:15:33.741 AudMan1 x2[2710:942837] device.name IB_A FOUND myPhoton=2f699a20 ``` ---
**Author:** ![douglaskbell](https://avatars.discourse-cdn.com/v4/letter/d/85e7bf/32.png) [@douglaskbell](https://community.particle.io/u/douglaskbell)\ **Post date:** [August 20, 2016, 1:22pm UTC](https://community.particle.io/t/cant-read-photon-firmware-variable-from-iphone-app-with-ios-cloud-sdk/25245/6 "2016-08-20T13:22:06Z")
So, I worked around the problem in the testButton() by moving the getVariable{} snippet into within getDevices{} where myPhoton is set, thus: ```auto ///////////////////// D E T E R M I N E O N L I N E D E V I C E S ///////////////////// printf("\n get specific device by name:\n" ); [[SparkCloud sharedInstance] getDevices: ^ (NSArray * sparkDevices, NSError * error) { printf("\n get specific device by name:\n" ); NSLog(@"%@", sparkDevices.description); // print all devices claimed to user // search for a specific device by name for (SparkDevice * device in sparkDevices) { if ([device.name isEqualToString:@"IB_A"]) // one of my Internet Button Photon's { myPhoton = device; NSLog(@"\n device.name %@ FOUND myPhoton=%x \n", device.name, myPhoton ); //////////////////////// R E A D D E V I C E B U T T O N /////////////////////// // reading a variable printf("\n reading a variable" ); [myPhoton getVariable:@"button_press" completion: ^ (id result, NSError * error) { printf("\n reading a variable" ); if (!error) { NSNumber* button_press = (NSNumber* )result; NSLog(@"button_press is #%f ", button_press.doubleValue); } else { NSLog(@"Failed reading button_press from Photon device"); } }]; } else { NSLog(@"\n device.name %@ NOT FOUND \n", device.name ); } } }]; ``` Why doesn’t the example app work as is? ---
**Author:** ![bko](https://sea2.discourse-cdn.com/flex026/user_avatar/community.particle.io/bko/32/20704_2.png) [@bko](https://community.particle.io/u/bko)\ **Post date:** [August 20, 2016, 2:28pm UTC](https://community.particle.io/t/cant-read-photon-firmware-variable-from-iphone-app-with-ios-cloud-sdk/25245/7 "2016-08-20T14:28:44Z")
> [@douglaskbell](#): > > void loop(){ > > ``` > // When you click the second button (at the 3 o'clock position) let's turn that LED on > if(b.buttonOn(1)) > { > button_press = 1; > Particle.variable( "button_press", button_press ); > > ``` Did you fix this part of your Photon code yet? You need to call Particle.variable during **setup()** not during **loop()** and only call it once. ---
**Author:** ![ScruffR](https://sea2.discourse-cdn.com/flex026/user_avatar/community.particle.io/scruffr/32/6952_2.png) [@ScruffR](https://community.particle.io/u/ScruffR)\ **Post date:** [August 20, 2016, 4:27pm UTC](https://community.particle.io/t/cant-read-photon-firmware-variable-from-iphone-app-with-ios-cloud-sdk/25245/8 "2016-08-20T16:27:12Z")
Yes, he said > [@douglaskbell](#): > > ScruffR: Correction made; Particle.variable() now only called once, in setup. ---
**Author:** ![Ric](https://sea2.discourse-cdn.com/flex026/user_avatar/community.particle.io/ric/32/514_2.png) [@Ric](https://community.particle.io/u/Ric)\ **Post date:** [August 20, 2016, 4:50pm UTC](https://community.particle.io/t/cant-read-photon-firmware-variable-from-iphone-app-with-ios-cloud-sdk/25245/9 "2016-08-20T16:50:13Z")
What’s happening is due to the asynchronous nature of the **getDevices** and **getVariable** methods. In the code you included in your previous post, you call **getVariable** outside the completion block of **getDevices**. Because **getDevices** is asynchronous, the method returns before the completion block is executed, and then **getDevices** is called immediately after; at this time, myPhoton will still be nil. In the code you have in your last post, you’re calling **getVariable** inside the completion block of **getDevices** , so it won’t run until that block gets executed. I haven’t looked at the example code you’re drawing from (I use my own code written in Swift), so I don’t know if that code works correctly or not, and that maybe it was your modification that caused it to not work. Where did you get the example from?