So far, I looked at the Si4332 and the S2LP Sub-GHz radio chips. I haven’t got them up and running yet. I have one more type of radio chip on a breakout board at home, a CC1101. I have ordered some HopeRF modules, RFM69 and RFM9x, which are SX1231 and SX127x based, according to adafruit. The datasheets check out. It looks the same datasheet with the branding replaced. Oh well…

I have designed some breakout boards for them, this time, in my new UEXT formfactor. I’ve used the 868 MHz PCB antenna, which is now in the KiCad library, based on a TI Design Note DN038 “swra416”. As a naive approach to make a 434 MHz version, I’ve doubled it’s size. I’ve put an RF connector on the board, so I can hook up my Nano VNA to see how it behaves so I can tune it. If all of this works out, I’ll make some boards for other modules as well. Having the same antenna and matching circuit on them makes it easier to compare the performance of the various chips/modules.

For now, there are a lot of radio modules in the picture, and therefore I present a table with some comparison

SPIRIT1 S2LP Si433x Si436x CC1101 SX1231 SX127x nRF905
150-174 MHz,
300-348 MHz,
387-470 MHz,
779-956 MHz
413-479 MHz (LPQTR)
452-527 MHz (LPCBQTR)
826-958 MHz (LPQTR)
904-1055 MHz (LPCBQTR)
240–930 MHz (Si4431/32)
900–960 MHz (Si4430)
119–1050 MH
300-348 MHz
387-464 MHz
779-928 MHz
290-340 Mhz
424- 510 Mhz
862-1020 Mhz
137 – 1020 MHz (SX1276)
137 – 1020 MHz (SX1276)
137 – 525 MHz (SX1278)
137 – 960MHz (SX1279)
430-928 Mhz
2FSK,
2GFSK
MSK
GMSK
OOK
ASK
2FSK
4FSK
2GFSK
4GFSK
OOK
ASK
2FSK
2GFSK
OOK
2FSK
4FSK
2GFSK
4GFSK
OOK
2FSK
4FSK
2GFSK
MSK
OOK
ASK
2FSK
2GFSK
MSK
GMSK
OOK
2FSK
2GFSK
MSK
GMSK
OOK,
LoRa
2GFSK,
1 to 500 kbps
0.1 to 500 kbps
0.123 to 256 kbps
100 bps to 1 Mbps
0.6 to 600 kbps
1.2 to 300 kbps
1.2 to 300 kbps
50 kbps

Note that this table is just an initial comparison based on the a quick glance at their datasheets. Most of these chips are highly configurable. The nRF905 is the exception, with a fixed datarate of 50 kbps, using 2GFSK modulation and Manchester encoding (thus the on-air datarate is 100 kbps).

All the other chips have many configuration options. They support various modulation types and datarates. One needs to configure the frequency, modulation, datarate, frequency deviation, bandwidth filter, and perhaps even more things to get these working properly. But having this flexibility also means they should be able to work together. So, in that case, I am not considering the nRF905, and look at all the other chips, I would suggest using the 2GFKS modulation. But well, that is for later concern. My little vacation is over, so I don’t know when I’ll have the time to continue.