I have small question about HM-10 ble module and master role.
I tried 2 scenarios.
Android app as master and hm-10 as slave:
From android app I can connect to hm-10 and its characteristic .
Everything works OK.
I have problem with second scenario: HM-10 as master and my ble device (LEGO SBRICK) as slave.
What I've done:
AT+ROLE1 - Set up to Central
Mode AT+IMME1 - Start from RESET
AT+SHOW1 - Show discovered devices
AT+DISC? - Discover Devices
AT+CON connect
Now my question is:
SBRICK is listening for ble command on service X and characteristic Y.
How can I send data from my HM-10 to specific characteristic of my SBRICK device ?
I can not find AT command for that.
I hope I didn't miss something from ble specification.
Any help please...
I am afraid there isn't an AT command to set a specific characteristic value.
The HM10 is a serial-port emulation device - It has a BLE characteristic, which displays all serial data (except AT commands). You will likely be able to find the service and characteristics details in the documentation (although I had a quick look and couldn't see anything).
So, data written to the serial port should appear as the value of that characteristic. Data written to that characteristic should be delivered out of the TX serial port pin on the HM10 module.
If you want to interrogate the device to find out it's serial and characteristic values, try using a debugging app - I use Light Blue on iOS, which will show all services and characteristics present on a device and show their properties and details.
pfodApp now supports BLE devices including HM-10. The free pfodDesigner lets you create custom custom Android menus and then generate the Arduino code for your particular hardware.
pfodApp supports data logging and plotting also.
Related
When connection to a custom BLE device from an app (android and ios) I have two options
a) first pair the device on the phone (like a headset or other devices) and then use it from the app to read and write data
b) without pairing on the phone, go inside the app, search for a device with a specific name or address, and just connect to it and read and write data.
when is one preferred over the other one ?
Its just when it needs to interact in the background or am I missing something?
The devices you see in your phones Bluetooth settings are Bluetooth Classic devices. There are some devices using both BLE and Bluetooth Classic which show up in the settings too, but the settings page is only for the Bluetooth Classic part of the device. Headphones for example are streaming music trough the Bluetooth Classic profile A2DP but might offer BLE services for additional features.
You always have to use a special app to communicate with the BLE part of a device. This could be an app provided by a manufacturer or a generic BLE scanner app such as nRF Connect.
As alexander.cpp already told you in his answer pairing (the exchange of keys) and bonding (saving of said keys) is not required for the communication with BLE devices and only needed if the device requires a secured connection.
Bonding (technically correct term for BLE, often called Pairing in non-technical speech) is mostly for security, we can send sensitive information because the receiver is verified and data is transferred in encrypted form.
Prefer to use bonding if the data is sensitive (means users feel uncomfortable if somebody they don't know receive their data). For example, I consider "current temperature = 25" as NOT sensitive. For detailed explanation, find "Bonding with a BLE device" in BLE guide by PunchThrough.
Also this is a good answer to a similar question: https://stackoverflow.com/a/42916081/10380092.
Your second question about background - no, bonding is not related to interaction in background.
I'm trying to establish a connection between my PC running Ubuntu and my iPhone via Bluetooth automatically when it becomes available, after being manually paired beforehand. I've seen this to be possible with certain peripherals, mainly audio. For example, my phone will automatically connect to a Bluetooth speaker when it is turned on and Bluetooth is active on my phone; another example is my phone automatically connects to my car's radio system via Bluetooth when I turn the car on.
I'm not able to connect my phone to my PC without first initiating the connection from the smartphone's Bluetooth menu. I'm thinking that I could possibly write an application for the PC to attempt to connect to the device every few minutes or something, but it seems that the phone needs to be the device to initiate the connection.
The only information that I need for what I'm trying to do ultimately is that the devices can pair successfully. Essentially I'm trying to build a sort of proximity trigger between my phone and my PC without using Wi-Fi and GPS - I can't use these for some specific reasons.
Is there any way to make this happen?
Yes this should be doable as long as you use the Background Processing feature for iOS apps. In the example I'll give below, we'll have the PC be the peripheral and the phone be the central, but you can really have it working either way. You will need to do the following:-
First initial connection needs to be performed in the foreground (this is due to iOS's background limitations).
On the iOS side, you need an application that acts as a central that scans and connects to the remove device (check this example as a starting point).
Upon connection, you need to bond with the PC. Bonding is important as it will prevent you from having to do the pairing again in the future. However, pairing/bonding is managed by the iPhone's OS so you cannot write it in your application, so the workaround is to have an encrypted characteristic on the PC side that will force the iPhone to bond (this is covered later).
On the PC side, you need to have a BlueZ script that acts as a peripheral that is always advertising. You can do this using bluetoothctl (check the examples here and here).
Before you start advertising, you need to have a GATT server on the PC side (to do this, check this example).
When registering characteristics, ensure that one of them has the encrypt-read property (you can find a full list of the properties here).
Now when you attempt to read this characteristic from the iOS side, the two devices should bond (make sure that your PC is bondable which you can do this via these commands).
Once the devices are paired, your iOS app needs to be working in the background constantly scanning and attempting to connect to the same peripheral (have a look at this and this example).
You can find more useful information at the links below:-
Getting started with Bluetooth Low Energy
The Ultimate Guide to CoreBluetooth Development
How to manage Bluetooth devices on Linux using bluetoothctl
I am currently having some issues with connecting to my peripheral. The bluetooth module in our peripheral does not seem to be advertising a name initially. I've have found that once I connect to the peripheral for the first time it will update the name and my scanner is then able to see the correct name.
I have no understanding why this is the case. I have also tried it using the Swift app we are developing, as well as a range of Bluetooth scanners on iOS and Android so I do not believe that this is an OS or programming error on the scanner side.
Is there a specific parameter that should be set on the peripheral. As I am just the app developer I do not have very much understanding about how the module is handing the process.
Any help would be much appreciated.
Just to confirm the scanner does not see a name for the peripheral until it has connected once. After this it will start displaying the name. Once the peripherals name is changed the old name is still being displayed until I have connected to it once again.
To display the name of device you need to see in advertisementData Dictionary which contains several keys depending on your device, in callback of didDiscoverPeripheral from CentralManager.
- (void)centralManager:(CBCentralManager *)central didDiscoverPeripheral:(CBPeripheral *)peripheral advertisementData:(NSDictionary<NSString *, id> *)advertisementData RSSI:(NSNumber *)RSSI
You can look for key CBAdvertisementDataLocalNameKey.
If you do not see the name, you can make changes in your firmware to include a name in GATT characteristic .
You can use LightBlue app to verify once. This is a good app on app-store to test your BLE device.
I am looking for a way to scan a device I own and discover "what it can do".
In other words, I'd like to know if a device is able to describe the way you have to communicate with it in order to build some application around it.
In my case it is a simple Christmas light that I'd like to play with but this could be used in different situations.
For classic bluetooth (BR/EDR):
When scanning for bluetooth devices (Inquiry), the bluetooth device will send an inquiry response (if it wants to be discovered) and maybe also an extended inquiry response (EIR). This EIR may already contain a list of services, the devices supports. This is a very fast way to get a picture of a remote device.
Moreover, the service discovery protocol (SDP) gives more information on a device. This takes some more steps. In SDP two devices can exchange their capabilites in kind of ping pong process.
For BLE:
After connecting a BLE device usually a service discovery takes place. The BLE peripheral (e.g. headset or a light) reports its capabilities to the central (e.g. smart phone). Some of these services have predefines functionalities. Additionally, it is free to the manufacturer to add custom services.
I have to test Ble devices with an App on iOS and Android, the scenario is having multiple device sending signals and it is difficult to figure out which device is connecting to what phone.
Is there a better way to test and what are some of best tools for checking the status of ble devices like signal strength and other characteristics.
I've been using LightBlue Explorer to poke at BLE devices to see characteristics and values. It can also emulate devices once it's seen a real one.
I ultimately ended up writing my own Device Simulator on iOS. This lets me generate a controlled BLE service/characteristic, with full control of the device name, advertised broadcast name, and characteristic values.