BLE error "BLE task REQ_DEV is already in progress"

[baldursigurds]

I have a Bangle.js 2 and a Puck.js, and I have previously connected from the bangle to the puck, either connecting to the bangle via the IDE, or directly, from an app that I wrote. Now, I do the same thing, and I get

Uncaught Error: BLE task REQ_DEV is already in progress

I don't know what changed, for this error to pop up. I'm running the exact same code that worked well a few weeks ago.

Some more details: one way I get the error is uploading the following code to the bangle via the ide

var uart;
NRF.requestDevice({ filters: [{ namePrefix: 'Puck.js' }] }).then(function(device) {
  return require("ble_uart").connect(device);
}).then(function(u) {
  uart = u;
  // Optional - wait 0.5 second for any data in the BLE buffer
  // to be sent - otherwise it may interfere with the result from
  // eval
  return new Promise(function(r) { setTimeout(r, 500); });
}).then(function() {
  return uart.eval('E.getTemperature()');
}).then(function(data) {
  print("Got temperature "+data);
  uart.disconnect();
});

which gives the error

>
Uncaught Error: BLE task REQ_DEV is already in progress
 at line 1 col 59
... namePrefix: 'Puck.js' }] }).then(function(device) {

Another way to get the same error is running the app calibrtr, available at a fork

https://github.com/baldursigurds/BangleApps

https://baldursigurds.github.io/BangleApps/?q=calibrtr

Running calibrtr with the IDE open gives

Uncaught Error: Unhandled promise rejection: Error: BLE task REQ_DEV is already in progress
 at line 38 col 75 in calibrtr.app.js
...s:[{namePrefix:"Puck.js"}]}).then(function(device){return require("ble_uart"...
                                           ^
in function called from line 39 col 91 in calibrtr.app.js
...));});uart.write(CODE);});});
                              ^
>

I have run this app several times (a few weeks / months ago) and obtained data via bluetooth. Now, the same code hangs on this error.

[gfwilliams]

Is it possible you may have uploaded To Flash on your Bangle with the IDE? In that case, some code could be running as well as your app, so effectively NRF.requestDevice( is being called two times, right next to each other?

The error BLE task REQ_DEV is already in progress basically only happens because NRF.requestDevice has previously been called and is still searching for whatever it was asked to search for last time.

You could paste this into the IDE:

require("Storage").list(undefined, {sf:false}).forEach(fn => {
  print("..."+fn);
   if (require("Storage").read(fn).includes("NRF.requestDevice"))
     print(fn+" contains NRF.requestDevice");
});

it'll take a while but will scan all files on the watch to see if anything you're not expecting includes a requestDevice call

[nravanelli]

Have you considered including a check to see if a scan is already happening? My current way to avoid this is to just run NRF.setScan(); before NRF.requestDevice(). This just feels dirty because I could be stopping another (important) scan.

perhaps a flag like NRF.ScanStatus()? True - scanning, False - not scanning.

[gfwilliams]

I think the scan is automatically stopped by requestdevice anyway? The REQ_DEV error is caused when someone has already called requestDevice before and it's still scanning.

I feel like it's better to error this way than to cancel the previous requestDevice call.

[nravanelli]

In my testing, I believe the second scan request errors out and does not go to the catch in the promise. Just tested using this basic function:

function NRFRequest(index){
  NRF.requestDevice({ timeout: 10000, active:true, filters: [{ namePrefix: 'Puck.js' }] }).then(function(device) {
    return device.gatt.connect();
    }).then(function(g) {
      gatt = g;
      return gatt.getPrimaryService("6e400001-b5a3-f393-e0a9-e50e24dcca9e");
    }).then(function(service) {
      return service.getCharacteristic("6e400002-b5a3-f393-e0a9-e50e24dcca9e");
    }).then(function(characteristic) {
      return characteristic.writeValue("LED1.set()\n");
    }).then(function() {
      gatt.disconnect();
      console.log("Done!");
    }).catch((e)=>{
        console.log(index, e);
        NRFRequest(index);
      });
}

NRFRequest(1);
setTimeout(function(){NRFRequest(2);},5000);

Log:

Uncaught Error: BLE task REQ_DEV is already in progress
 at line 1 col 76
...s:[{namePrefix:"Puck.js"}]}).then(function(device){return device.gatt.con...
                                           ^
in function "NRFRequest" called from line 1 col 13
NRFRequest(2);
            ^
in function called from system
1 No device found matching filters
1 No device found matching filters
1 No device found matching filters
1 No device found matching filters
1 No device found matching filters
1 No device found matching filters
1 No device found matching filters
1 No device found matching filters
1 No device found matching filters
1 No device found matching filters
1 No device found matching filters
1 No device found matching filters
1 No device found matching filters
1 No device found matching filters
1 No device found matching filters
1 No device found matching filters
1 No device found matching filters
1 No device found matching filters

[gfwilliams]

Yes, that's correct. It errors on the call rather than in the returned promise - at the time it was intentional as it means you actually get a proper stack trace pointing to the error (which doesn't always happen for promises) - but maybe that should be changed at some point

[baldursigurds]

Thanks a bunch! I tried running the code and found hits on bthrm, as well as two apps I've written. I tried uninstalling the three apps and now it works. I reinstalled the apps, and it still works. Unfortunately I do not know which part of this procedure fixed the problem, i.e. where the problem lay. I'll try to be more methodical if this happens again, to try to actually find the problem.