can an nrf52 series SOC transmite a ble message to 150 units in one second ?

RE: can an nrf52 series SOC transmite a ble message to 150 units in one second ?

Dmitry — Mon, 22 Jun 2020 09:26:06 GMT

Hi,

[quote userid="90084" url="~/f/nordic-q-a/62656/can-an-nrf52-series-soc-transmite-a-ble-message-to-150-units-in-one-second/256082"]I am a bit confused.. when referring to a 255 byte of data size in a packet, are we referring to a beacon packet or a broadcasting packet (does it metter? are they both runing over the 3 advertising channels? ) ?[/quote]

I can't get what you mean under 'broadcasting packet', but any packed can't be longer than 255 bytes - it's a hardware limitation. You can set channel mask to advertise only on a single channel.

[quote userid="90084" url="~/f/nordic-q-a/62656/can-an-nrf52-series-soc-transmite-a-ble-message-to-150-units-in-one-second/256082"]When talking about time slots do you mean after pairing has been made ( i guess it is configured within the GATT) ?[/quote]

I mean a custom protocol that would use radio directly - no GATT and pairing, you can define timings and packet content as you wish (again, not longer than 255 bytes). The drawback is lack of security (if you're concerned with it) and higher complexity of development.

[quote userid="90084" url="~/f/nordic-q-a/62656/can-an-nrf52-series-soc-transmite-a-ble-message-to-150-units-in-one-second/256082"]If I wish to send a 255 byte packet from my nrf52832, how many packets like that I can broadcast in one second ? I think I need at least 15, to 3 different units groups ids ?[/quote]

With BLE advertising, you're limited with minimal interval that is 20 msec - you can send about 50 messages in a second (with extended advertisings, a message can consist of more than one packet, up to 1650 bytes).

[quote userid="90084" url="~/f/nordic-q-a/62656/can-an-nrf52-series-soc-transmite-a-ble-message-to-150-units-in-one-second/256082"]and is there an sdk example or certain softdevice that support Bluetooth instead of ble ?[/quote]

BLE is Bluetooth Low Energy, under Bluetooth 5.0 I mean its low energy variant. We're not talking about classic Bluetooth - it's not supported by nrf52.

RE: can an nrf52 series SOC transmite a ble message to 150 units in one second ?

ziv123 — Mon, 22 Jun 2020 06:12:21 GMT

I am a bit confused.. when referring to a 255 byte of data size in a packet, are we referring to a beacon packet or a broadcasting packet (does it metter? are they both runing over the 3 advertising channels? ) ?

When talking about time slots do you mean after pairing has been made ( i guess it is configured within the GATT) ?

I am not planning on pairing because I want to send the message from one unit to all the rest (its like an initiating central to many peripheral) and I don't want to loos time on scanning Acks and such.

If I wish to send a 255 byte packet from my nrf52832, how many packets like that I can broadcast in one second ? I think I need at least 15, to 3 different units groups ids ?

is it preferable to use Bluetooth 5.0 if i have no power supply issues ?

if Bluetooth is preferable then why and does it have a brodcast mode like beacon or other to transmit data to all listeners?

and is there an sdk example or certain softdevice that support Bluetooth instead of ble ?

Best regards

Ziv

RE: can an nrf52 series SOC transmite a ble message to 150 units in one second ?

Dmitry — Wed, 17 Jun 2020 09:46:09 GMT

[quote userid="90084" url="~/f/nordic-q-a/62656/can-an-nrf52-series-soc-transmite-a-ble-message-to-150-units-in-one-second/255409"]well i was thinking of grouping 50 messages in a packet (not sure how long this packet needs to be in that case)[/quote]

A single packet cannot be longer than 255 bytes - you can group up to 8 devices into a message, but in case of a single error, the whole message will be lost.

[quote userid="90084" url="~/f/nordic-q-a/62656/can-an-nrf52-series-soc-transmite-a-ble-message-to-150-units-in-one-second/255409"]what did you mean by different time slots for each receiver[/quote]

When using own protocol, you can divide 1 second into 150 timeslots, sending a message for each device with different access address at exact point of time.

[quote userid="90084" url="~/f/nordic-q-a/62656/can-an-nrf52-series-soc-transmite-a-ble-message-to-150-units-in-one-second/255409"] i don't have a shared clock or something like that[/quote]

I don't know your case in detail, an easiest way is to listen continuously until first packet with receiver's access address arrived, then start RX every time a bit ahead of its next timeslot (knowing that there should be exactly 1000 ms from start to start).

RE: can an nrf52 series SOC transmite a ble message to 150 units in one second ?

ziv123 — Wed, 17 Jun 2020 07:20:23 GMT

hi Dmitry

well i was thinking of grouping 50 messages in a packet (not sure how long this packet needs to be in that case) and then send 3 messages in one second, but i guess there can be some deviation which is best .. what did you mean by different time slots for each receiver, it is an asynch communication, i don't have a shared clock or something like that, how is that possible to have different time slots for each receiver group to start listening at the correct time within the every second ?

RE: can an nrf52 series SOC transmite a ble message to 150 units in one second ?

Dmitry — Tue, 16 Jun 2020 21:15:08 GMT

Bluetooth 5 is a good idea - not only because of longer messages, but because you can offload your data to secondary channels and not spam too much at primary ones. Remember, the longer your message, the higher probability to have a bit error somewhere and loose the whole packet.

Grouping messages by 3 in a packet, you will need to send 50 messages per second, not a problem.. but think about other side - every device should listen continuously, receive and analyze each message, taking radio and CPU busy most of the time. Maybe it worth to think about custom protocol with different time slots for each receiver. Though if your devices are not battery-powered, it's not an issue.

RE: can an nrf52 series SOC transmite a ble message to 150 units in one second ?

awneil — Tue, 16 Jun 2020 16:25:10 GMT

yes, that sounds like a good idea.

If you can't pack it all into a single message, perhaps you could divide the receivers into a number of groups - and apply this scheme per group. eg, 10 groups of 15 (an nRF52832 can do 20 connections at once, IIRC)

RE: can an nrf52 series SOC transmite a ble message to 150 units in one second ?

awneil — Tue, 16 Jun 2020 16:20:31 GMT

So that's not "broadcasting", then - is it?

RE: can an nrf52 series SOC transmite a ble message to 150 units in one second ?

ziv123 — Tue, 16 Jun 2020 16:11:53 GMT

thinking about it ...

an elegant solution could be to send one message, each unit receives the same message but takes its own relevant data by byte position or some "pre-unit id" info .. need to check the maximum number of bytes possible to deliver via ble or bleutooth 5

RE: can an nrf52 series SOC transmite a ble message to 150 units in one second ?

ziv123 — Tue, 16 Jun 2020 16:02:18 GMT

this is not what i asked... i know when you send a beacon everybody in the area can scan for it but i want to send different messages to different units, which i design as well, i don't want to create the pear to pear connection because i asume that will take to much time, each unit will read its own id in the message

but the main unit needs to be sending 150 different messages in one seconds that was my question

regarding the dupilcate.. i send the same question one for hardware and one for software i thought it goes to different supporter engineers from nordic

RE: can an nrf52 series SOC transmite a ble message to 150 units in one second ?

awneil — Tue, 16 Jun 2020 15:52:54 GMT

If you're broadcasting, as a beacon, then you have no idea how many devices are listening - it is essentially unlimited.

EDIT

AHA: it is a duplicate - not just the forum losing replies:

https://devzone.nordicsemi.com/f/nordic-q-a/62657/can-an-nrf52-series-soc-transmite-a-ble-message-to-150-units-in-one-second