Idea for Crossbow, DIY LRS system did not appearned in my mind out of nowhere. All my previous LoRa attempts were aimed at telemetry purposes only. E45-TTL-100 are cool, but bulky. If I would want to use them, I would either have to attach Arduino to it or hack it open and reprogram onboard CPU (like Qczek LRS does). Somehow it was not something what suited me very much.
But then I came across Adafruit Feather LoRa32u4 RFM95. Awesome idea. ATmega32u4 and HopeRF RFM95 LoRa module on one PCB, Arduino compatible, reasonably small and light. As a bonus, can be LiPo battery operated and has own 1S LiPo chanrger. The only thing I did not liked (OK, not the only one, but that was the biggest one) was price tag: $34.95 is somehow slightly more than I’m willing to pay for ATmega32u4. Even with radio module. So, after some digging on eBay I’ve found something that looked like a clone of Adafruit Feather LoRa32u4 RFM95: BSFrance LoRa32u4 II.
LoRa32u4 II 868MHz LoRa development board
I’ve called LoRa32u4 II a clone of Feather LoRa32u4 but perhaps this is not a correct word. OK, it looks like the same board layout, CPU, and so on, but someone had put some effort into proper branding. There is a separate board definition for Arduino. So, I think it is OK to call it an independent product after all.
- ATmega32u4 is running at 3.3V and 8MHz
- All pins are 3.3V, 5V will fry the CPU
- Onboard RF module is Semtech SX1276 based Shenzhen HPD13-868 (HopeRF RFM95W compatible)
- There are both soldering pad and u.fl connector for antenna
- RF module is connected via SPI bus plus:
- SS pin: 8
- RST pin: 4
- DIO0 pin: 7
- Board can be powered directly from 1S LiPo battery connected via JST connector
- LoRa32u4 has build in 1S LiPo charger. Charger works only when boards is powered from USB or 5V pin
- There is no RAW input, that means it can operate only from 3.3V or 5V external power supply
- Board can be used directly with Arduino when this board definition is installed. Just unzip it to
Arduino/hardwarefolder that it contains
- LoRa RF module can be programmed using Arduino LoRa library
- Beware of antennas! u.fl 868MHz antennas I received when ordering those boards from ebay (seller DIYmall) were not 868MHz! Just use 80mm of copper wire soldered to ANT pad and you will be fine