Why SPSGRF-868?


#1

Hi,
I quickly looked at core module schematic and price of minimum necessary componets. Radio module SPSGRF-868 costs (approx) as much as all other components together. So, it doubles total module price…

I’m wondering, why you decided to choose this radio module? Because of integrated features? Or you have already some experiences with this one? Or is the cheapest on the market? (I’m new to embedding wireless communication)

Background: I’m thinking about possibility to create custom version of core module hardware, compatible with your sw but with fixed features, minimum componets, single-purpose and as cheap as possible.


#2

Hello Kapitan,
I try to answer your question now, but I hope that our HW development leader @hubpav also adds something.

The main feature of our modules is the RF communication. We need robustness, reliability and low power so we cannot save on the price here.
In the early days of BigClown the hardware team had a lot of meetings with different manufacturers and also they had a lot of experience from previous company where they used radio communication. All this knowledge and lot of decisions went to the final selection for SPIRIT1. It has lot of features for reliable communication (e.g. antenna diversity algorithm). It’s also great for low power applications.
It’s definitely not the cheapest solution :slight_smile:

I’m glad that BigClown used this radio. One year ago when I wasn’t part of the BC I was experimenting with a lot of solutions. RAW 2,4GHz packets (NRF24L01+) or WiFi with ESP8266 which was not reliable.
When I get Core Module I did some tests and one receiver really covered all my house and even the bigger garden. I tried to go to the furthest corner of the garden, block the signal with my body and even when I hold my fingers on the antenna - the packet was sent without an issue. That amazed me.

We would like to hear more about your idea of smaller and cheaper module based on Bigclown parts. Our plan is to design the USB dongle which will be smaller and without necessary connectors, accelerometer and thermometer. This dongle will act as a gateway.

The second direction we are thinking is “Compute Module” with castellated edges like this SparkFun module. Compute module can be easily soldered on your own board and routed even with single layer PCB. I’m not sure when these modules will be designed. There’s already a lot of work and directions with our current portfolio and the resources are not infinite.

Where you would like to use your custom low cost core module version? Will it be open-source? We can cooperate and help you with design or even produce some prototypes.


#3

Thanks Martin, you have pretty much covered all the reasons.

I will just point out that we do not use antenna diversity (you need two antennas for that).

It is also worth emphasizing that it all comes down to reliability. SPIRIT1 has good blocking immunity and its RF parameters are out-performing many other “Sub-GHz” radios. Speaking the frequency band itself (868 MHz), the choice has been pretty obvious to us - 2.4 GHz band is very polluted from Bluetooth, WiFi, ZigBee, etc. and going down with frequency and bandwidth means you get lower power requirements (longer battery life time) and longer communication distance.

I agree we could have done it cheaper by not using SPSGRF module but using chipset with crystal, balun, antenna and other components directly assembled on Core Module but this is already pre-certfified solution and it represented quick time to market delivery at the time we decided to develop Core Module.


#4

Thanks both for answering me.

I think, small USB dongle gateway is “must have”, so hurry up :wink:

Some time before, I was searching for small wireless module, which I can place (stick) wherever I want and sens things remotely. Collect all data, examine and maybe do some (home) automation on it. My requirements was:

  1. Battery powered. (from single button cell, but for some application maybe external powered…)
  2. Small. Very small.
  3. Able to sense: digital input, impulse input, temperature, humidity, …
  4. Cheap. Very cheap. (as I need many modules and budget is always small)

As I did not find any product which meets my needs, I decided to build my own. As universal module will never be small and cheap (like BC Core+Battery+Tag+Tags modules), many variants of PCB with single purpose may be the answer.

ESP8266 was very promising. Very small and very cheap chip, with possibility to implement simple single purpose software right inside it - so no additional parts needed. Against it was custom PCB design of radio part (which is behind my knowledge) and mainly that it is not very good choice or battery applications…

Then I found BigClown project and I like it’s open idea. So I delayed my plans until some first products was published. Finally I was a little bit disappointed with first hardware modules (Bridge+Tag), because it was’t usable for me. Then I waited again for first wireless module, but…it was big (both size&price:)

It seems that BigClown project is still in starting phase, so maybe there is some space to play also with (side) ideas like mine.

Basic idea of single purpose wireless module based on BC Core Module:

  • 1x MCU
  • 1x RADIO
  • 1x AUTH
  • 1x LED
  • 1x Power supply circuit (battery/external powered 5/12V)
  • 1x power connector (or only soldering pads)
  • 1x connector for IO (or only soldering pads)
  • 1x passive parts for simple IO, one of:
  • digital input (for NO/NC contact, magnetic contact, optical sensor, etc)
  • digital input 230V
  • temperature sensor
  • humidity sensor
  • digital output (FET/SSR, for externaly powered version)
  • digital output (230V Relay, for externaly powered version)
  • UART interface (TTL)

I think that HW like this may be (hope)fully compatible with SW for original BC Core Module.


#5

Hi…i am a new user here. In my case I did some tests and one receiver really covered all my rooms. I tried to go to the furthest corner of the house, block the signal with my body and even when I hold my fingers on the antenna and the packet was sent without an issue.