DK research for multiple transmitters to one receiver in fixed pair for health and fitness

[Alessio]

Goodmorning,

we are looking for a development kit to test the transmission for the following purpose.
We need a system with one receiver and some transmitters (up to 5) to develop Health/fitness sensors and monitor devices.
The idea is that all the sensor devices, that are acquiring different data, are paired in a fixed way with a single receiver which is collecting data from sensors and send them to the PC over USB.
Each sensor send a new value every 10ms, so the receiver needs to be fast enought to receive them.
All the sensor devices (transmitters) must be movable. All the system is intended to be used INDOOR (in a single room) or OUTDOOR.
All the devices has to be as small as possible, so it's better to use PCB antennas.

We had already try this with nRF24 series without success: the transmission data is not robust and the data are lost frequently even at short distance between transmitter and receiver, in one-to-one or in a more-to-one configuration/network. You can verify the situation by the tikets opened in your on-line technical support service.

Please is there some new device suitable for this application? Can you advise us some DK?
Along with the hypothetic DK, do you have a firmware/software ready to go that we can use to test the transmission? It doesn't care what data it transmits and where they are coming from.
Just something to test the reception of the amount of data we need without wasting time on code writing, we already spent lot of time with nRF24.

Thanks.

[Edvin]

Goodmorning!

 

Each sensor send a new value every 10ms, so the receiver needs to be fast enought to receive them.

 Does that mean that you need maximum 10ms latency, or would the double (20ms) latency be fine?

The reason I ask is because it may be difficult to fit 5 BLE connections within 10ms, but 20 should be possible.

We don't have an application that already does exactly this, but the nRF52840 DK or the nRF52833 DK has the USB peripheral. For the devices that doesn't require USB you can use the nRF52832, or possibly the nRF52811, if the application isn't very demanding.

For your application I would suggest a couple of applications.

ble_app_blinky for remote devices and ble_app_multilink_central for the USB device. This example set is already capable of one central with up to 8 peripherals.

ble_app_uart for remote devices and ble_app_uart_c for the USB device. This example use a more flexible BLE service, which you can send data through.

So by changing the BLE service in the blinky/multilink example to the uart service (NUS/Nordic UART Service), you can have a one to many connection. In addition, you would need to change the UART with USB in the central, so that it will transmit the data over USB instead of UART. For this, please check out the example found in

SDK\examples\peripheral\usbd_cdc_acm.

Best regards,

Edvin

[Alessio]

Goodmorning,

Regarding the 10ms topic, if the devices are only 3, is it possible to fit them into 10ms? What is the max number of devices connectable at 10ms interval data transfer?

Between the two application you suggest, what's the difference between them? I understand that the first example is capable of many to one, why do we need to change the protocol?
Please change the comunication from UART to USB, We already spent a lot of time on programming kits of nRF24 to configure them to works to comunication by USB, time spent for nothing because the nRF24 have severe problem with WIFI communication!

Finally, regardig the application, can you develop an example that fit what we need? We already spent money to try to resolve wifi comunication problems and buying kits of nRF24 without success.

Thanks.

[Edvin]

Alessio said:

Between the two application you suggest, what's the difference between them? I understand that the first example is capable of many to one, why do we need to change the protocol?

 The many-to-one example only use a BLE service that has an on-off bit, like a light switch, while the ble_app_uart example simulates a serial UART connection over BLE. So the last one is useful for sending custom data. You may even want to customize your own BLE service in the end, which you are free to do. 

 

Alessio said:

Regarding the 10ms topic, if the devices are only 3, is it possible to fit them into 10ms? What is the max number of devices connectable at 10ms interval data transfer?

 This depends on how much data you intend to send. Check out the online power profiler. If you set the role to Connected(central) mode, you can change the amount of data that you send, and you can see in the graph how much time it uses the radio for that data for one link.

With no payload (0), it takes 2.5ms to handle one connection. With 244 bytes it takes a little more than 4 ms.

 

Alessio said:

Finally, regardig the application, can you develop an example that fit what we need? We already spent money to try to resolve wifi comunication problems and buying kits of nRF24 without success.

 I am sorry. We can't deliver this service. If you want on site help, like this, you need to discuss this with the Regional Sales Manager (RSM) for your area (Italy, right?). Perhaps they can suggest someone for you. Let me know if you want the contact information to your RSM by sending me a PM here on DevZone.

[Alessio]

Hi,

When I send 244Byte, the 4 ms time includes the 2,5 ms time?

Can you exaplain what means payload=0? Is the time that the receiver takes to identifing if the data transmitted are from a trusted transmitter?

What do you mean with "PM"? In any case, yes, I prefer to discuss with the RSM to save my time and money to complete a full functionally demo.

We ask you for the best solution, you had suggest us more than one devices. Which is the best for our application? You didn't tell us what are the main differences between the devices suggested.

[Edvin]

Alessio said:

When I send 244Byte, the 4 ms time includes the 2,5 ms time?

 Yes. Check out the online power profiler. You will see the graphs.

 

Alessio said:

Can you exaplain what means payload=0? Is the time that the receiver takes to identifing if the data transmitted are from a trusted transmitter?

 When you don't send any data, there are still packets being sent between the devices every connection interval. These "empty" packets contain some headers and event IDs (part of the BLE specification). They are also used for synchronizing the timing between the devices, to prevent drift. So the packets are not actually empty, but they do not contain any application payload. 

Alessio said:

What do you mean with "PM"? In any case, yes, I prefer to discuss with the RSM to save my time and money to complete a full functionally demo.

 Send me a Personal Message, and I can reply with the contact information of the RSM. I can't give it here in a public ticket.

The reason you must do this is that you can't send messages to accounts that you aren't "friends with" on DevZone, unless that user has opened up for messages for anyone. I have done this, but I can't send a message to you unless you send one to me first.

You can send a message like this:

Alessio said:

We ask you for the best solution, you had suggest us more than one devices. Which is the best for our application? You didn't tell us what are the main differences between the devices suggested.

 

If you are not very experienced with embedded controllers, and you want as little issues as possible, order 2x nRF52840 DK, and follow the examples that I mentioned.

BR,

Edvin