The SX127x family of chips from Semtech are modems supporting both LoRa and (G)FSK modulations (including ultra-narrow band FSK). Coupled with a microcontroller implementing the relevant stack(s), they are already used for with following IoT network protocols: LoRaWAN, Sigfox, Wireless M-Bus, DASH7 and Symphony Link. They could probably also be used with ...
Unfortunately this is not a complete answer, I will update it if I get more information. As for now, based on the Sigfox AT command descriptions.
AT$SB=bit[.bit] Send a Bit Status (0 or 1).
to send payload data or frame of size 1 to 12 bytes. For example:
SB means Status Bit message
SF means Sigfox ...
I would suggest using LoRaWAN connectivity, that offers a scalable network infrastructure for several hundred/thousands/millions of devices. For that, you need to deploy the LoRaWAN protocol stack on your stm32 and connect it to a community operated LoRaWAN network like Loriot, Actility ThingPark or TTN. Your selected LoRaWAN network can easiliy be ...
It's all documented in the Sigfox device radio specifications. For an uplink:
19 bits preamble
13 bits frame type
2 bits length indicator
1 bit bidirectional frag
1 bit repeated flag
12 bits message counter
32 bits identifier
variable length uplink authentication (between 2 and 5 bytes)
16 bits CRC
Which gives a total of 112 to 136 bits, 14 to 17 bytes.
Be aware that with LoRaWAN (and others ISM technologies), you have to follow the local regulation about duty cycle as you will use ISM radio band.
If you are at a distance of around 5km, you may need to use a large spreading factor meaning you will spread the data on air, and so use more airtime.
In Europe, you have (basically) 1% of air time allow. See ...
I did a case study on LoRaWAN in 2015. Since then the community is continuously growing. The case study was about installing one Gateway in our city.
I find it one of the best solution because
Low power consumption (As a node reports to Gateway, 3 AAA batteries lasts for more than a month)
Low cost devices (The Things Uno)
Long range wireless network (Up ...