Author Topic: Bluetooth LE choosing the right module  (Read 295 times)

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Offline TimB100

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Bluetooth LE choosing the right module
« on: October 22, 2020, 07:26:56 am »

First off thanks to those who helped me see the light in the last days with BT LE.

One of the devices I need BLE on is a temperature meter that talks to an app (android or PC etc) via Bluetooth LE. Originally I wanted to be able to talk back to the temp meter. I have given up on that now as the use cases are really really small and not worth the effort.

I'm now just looking to broadcast the data every 1hz and the app if its listening will collect the data. The 32 bytes payload I see is fine for what I need.

I'm now trying to figure out what module to use. Price around £7 or less so that rules in most I have seen. Having spent so much time and money on Dev work so far I'm burnt out on doing massive amounts of reading (reading is not a strong point of mine  :( ). So I'm here with cap in hand looking for advice.

Requirements
1 Simple config
2 Simple interface eg Usart or SPI
3 Simple just send the data and the BLE will broadcast it. Really that simple

Can anyone recommend a module
As an aside the numbers I will probably sell are tiny (25 perhaps a year) so I will not CE test my electronics but the modules will need to be pre- certified.
 

Offline DrG

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Re: Bluetooth LE choosing the right module
« Reply #1 on: October 22, 2020, 04:11:52 pm »

First off thanks to those who helped me see the light in the last days with BT LE.

One of the devices I need BLE on is a temperature meter that talks to an app (android or PC etc) via Bluetooth LE. Originally I wanted to be able to talk back to the temp meter. I have given up on that now as the use cases are really really small and not worth the effort.

I'm now just looking to broadcast the data every 1hz and the app if its listening will collect the data. The 32 bytes payload I see is fine for what I need.

I'm now trying to figure out what module to use. Price around £7 or less so that rules in most I have seen. Having spent so much time and money on Dev work so far I'm burnt out on doing massive amounts of reading (reading is not a strong point of mine  :( ). So I'm here with cap in hand looking for advice.

Requirements
1 Simple config
2 Simple interface eg Usart or SPI
3 Simple just send the data and the BLE will broadcast it. Really that simple

Can anyone recommend a module
As an aside the numbers I will probably sell are tiny (25 perhaps a year) so I will not CE test my electronics but the modules will need to be pre- certified.

Your requirements have the word "simple" four times".  ;D

I think you are describing a BLE beacon. These simply broadcast some information (an advertisement) whether anyone is listening or not. Nothing connects to them. But, since you can program what is being broadcast, they can have more information beyond "I am here and talking". The Beacon advertisement is not as universal as one might think. After some background reading on what a beacon advertisement is made up of (e.g., https://os.mbed.com/blog/entry/BLE-Beacons-URIBeacon-AltBeacons-iBeacon/ ; https://www.ti.com/lit/ug/tiducd0/tiducd0.pdf?ts=1603382571514&ref_url=https%253A%252F%252Fwww.google.com%252F ).

You may want to take a look at these https://www.tme.com/Document/270cd78e34a295f23f07653544e908b8/CYALKIT-E03_SOLAR-POWERED.pdf They are about US$20 each and may not fit your budget, but I think they are worth looking at to get an idea of how to implement your requirements. I have used these and have read them with several controllers (including an ESP32). I Never wrote an Android app for them but the developer kit has one in the software.

What is particularly nice about these is the solar cell PS (and associated "harvesting" chip which charges an onboard capacitor. If it has been in bright light (even close to a bright indoor light), which is on, for say 12 hours, it can usually hold a charge until the lights come on again. Of course, that is dependent on advertising frequency. Unless you program these yourself, you are stuck with their advertising frequency (which varies - actually there are two modes).

You can also add a 3V cell which can be used when the onboard cap is not holding a charge.

I don't mean to suggest that these are an off-the-shelf solution that meets your requirements, but the data and app notes around the product can serve as a reasonable introduction to the subject. These have temp and humidity (and they annoyingly decreased transmitted resolution) values that are advertised in place of the "minor ID" field (a specific field in the beacon advertisement).

So, ONE basic strategy is to identify the Beacon using the UUID and then identify the specific unit using the Major ID and then get the temperature value from the minor ID field.

Again, not necessarily an off-the-shelf solution but worth looking into in my opinion.
- Invest in science - it pays big dividends. -
 

Offline Evan.Cornell

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Re: Bluetooth LE choosing the right module
« Reply #2 on: October 22, 2020, 08:24:57 pm »
https://www.ti.com/tool/TIDA-00374 This is such an application; broadcast temp & humidity sensor info in advertisement packet once per minute.
 


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