RF product recommandation

[tatulea]

Hi,

I have to do a wireless accelerometer. This means that I will have an MPU9250, an Arduino (for testing) and I need a way to transmit the values from the accelerometer to the internet. The device should be wearable. I want to send about 50KB per second. There will be more devices and they will be used in factory environment. My question is that technology should I use to send data (2.4GHz, sub GHz..)?

Thanks

[Bjørn Kvaale]

Are you planning on hooking up the Arduino device to the MPU9250? This seems like a good use case for Bluetooth Low Energy. You are sending quite a lot of data, but that should work if you use Bluetooth 5 for example. With the new high speed throughput example, we have tested 1400 kbps. When you are sending at such a high data rate, the current consumption will naturally be higher than when you are sending at a lower data rate.

Also, with Bluetooth 5 there is improved coexistence in noisy environments by using a new channel mapping algorithm for improved channel hopping sequencing. All nRF52 devices support this new algorithm.

I would recommend getting an nRF52 dev kit instead of an Arduino if you want to ask for more help on our DevZone. We have a lot more experience with the dev kits than Arduino Primo for example (which has a 52 dev kit inside).

An application engineer from Nordic has also written some demo examples that work for the MPU9255 & might also work for the 9250 model that you are using.

[tatulea]

Thanks! Yes, I am planning to use Arduino and MPU9250, but just for testing.

What range should I expect for Bluetooth 5 at this rate? How many devices can I connect to a single gateway? I may have more than 20 devices in the same factory, but I can install more gateways.

Is there any other solution that I can look into? What about the sub GHz?

[Bjørn Kvaale]

Which Arduino are you planning on using? Regarding range, you will need to test this yourself. The range can vary a lot depending on the environment you are in & wireless interference from other devices. You can take a look at this blog post for more information regarding this. If you choose to use a 52832 or 52840 device, you can have up to 20 concurrent connections. I would not recommend using sub GHz for a new design.

[tatulea]

I would like to try with Arduino Uno firstly. I ordered a 52840 DK. The 52840 dongle should be good to test the connection, rate and range?

You said I can use 20 concurrent connections, but for what protocol? Bluetooth 5?

Also, what about Nordic 2.4 proprietary protocol?

[Bjørn Kvaale]

20 concurrent connections can be used with Bluetooth 5 yes. I am not too familiar with Nordic 2.4. GHz proprietary protocols, but I would recommend sticking with the regular BLE (e.g. Bluetooth 5).

You can test examples on the 52840 dongle, but it is most likely easier to use two dev kits to start testing the BLE connection. You can see which examples are supported out of the box if you search for pca10059 in the sdk 15.1 examples folder. The dongle is useful as a sniffer for BLE connections for example in the nRF Connect for Desktop app. If you take a look at the product page for the dongle, you can see this line: "For other use cases please do note that there is no debug support on the Dongle, only support for programming the device and communicating through USB."

Therefore, it is most likely easier to use two dev kits. Remember to buy two 52840 dev kits if you want to test long range.