32U4 microcontroler + Radio Module Radio to create 868 MHz telemetric measurement with the RFM69HCW
It would be really great to transport the data over a long distance. Thank to the radiofruit module, it is now possible :-). This radiofruit product combines a microcontroler with a packet radio module board. In the hand, you have micro system ready to collect and send data over the air.
This product contains a Feather 32U4 (like the Arduino Micro) and a RFM69HCW ranged for 868 MHz frequencies! It modulates packet radio data with FSK modulation +20dBm including some extra like encryption & auto-retransmit. With a single wire antenna, it is already possible to send data up to 350m (free line of sight). When using a directional antenna and tuning parameters, it is possible to impressively increase the distance of transmission.
The well known Feather is an Adafruit's development plateform designed for microcontroler's based embeded project. Feather are thin, light and incredibly small. Feather did rapidly becames a new standard for embeded projects and we have toons of Feather and FeatherWings on our shop.
This feather version is assembled for radio transmission @ 868 MHz radio version. The exact radio frequency is set when the software is loaded (and can be tuned dynamically). Note that it also exists in 433 MHz flavor!
This board is propelled an Atmel 32u4 (3.3v logic) clocked at 8 MHz, this processor is very popular in the Arduino world and the same as the Flora plateform. The 32u4 have 32KiB of Flash and 2KiB of RAM. This microcontroler does have a native USB support so USB-to-Serial program & debug capability are included inside the 32U4 and there is no need for an additional FTDI-like chip. Thanks to the USB support, the 32U4 can act as mouse, keyboard, USB MIDI device, etc.
Embeded and portable project need to power! Adafruit did added a LiPo charger circuitery and a connector for 3.7V Lithium polymer batteries. The battery is not a mandatory to make the Feather running. When a Lipo is connected, it is charged when the board is connected on USB. When the USB connexion is removed then LiPo battery would immediately power up the board from le LiPo. The plateform supply automagically switch from the USB power to Lipo power.
The battery is tie to an analog pin through a resistor divider, so it is possible you can measure and monitor the battery voltage to detect when it needs to recharge.
About radio transmission
The transmission of packet radio is simplier than WiFi or Bluetooth Low Energy (BLE). No need for networks scanning, pairing or WiFi network configuration. With packet Radio, you can transmit data over the air without worry about pairing or WiFi connexion. All the other module listening on the same frequency (and encryption key) can receive the messages. Then the receiver can send an acknowledgment response
The board is fit with extra specialized breakout that cares about packet handling, auto-restransmit and error correction.
The breakout does work great with microcontrolers (like Arduino), you can use it to connect data in the neigbbordhood (or in the town). The constraint with such radio moduie is that you need 2 of them (emitter and receiver, but you are free to use more breakouts as needed) sharing the same frequency.
The radio packet modules does exists in 4 combinations:
- 2 modulation KIND: RFM69 & LoRa
- 2 frequency: 433 Mhz & 900 Mhz
The RFM69 modules are the easiest to use. RFM69 is very well known (LoRa is mode powerfull but also more expensive).
- Size: 51mm x 23mm x 8mm (without headers)
- Weight: 5.5 grams
- ATmega32u4 @ 8MHz with 3.3V logic/power
- 3.3V regulator with 500mA peak current output
- USB native support, comes with USB bootloader and serial port debugging
- 20 GPIO pins
- 7 x PWM pins
- 10 x analog inputs
- Hardware Serial, hardware I2C, hardware SPI support
- Built in 100mA lipoly charger with charging status indicator LED
- Pin #13 red LED for general purpose blinking
- Power/enable pin
- 4 mounting holes
- Reset button
- RFM69HCW datasheet (inclus SX1231 datasheet)
The Feather 32U4 Radio have extra space left, enough to receives the RFM69HCW 868MHz radio module... so radio module is included onto the board. Please note that RFM69 is not designed for high throuput! So you can easily send telemetric data but not audio and video streams. RFM69 and packet radio will save you lot of effort when you need to transport data quite over the distance range of 2.4 GHz devices (BT, BLE, WiFi, ZigBee)
- RadioFruit breakout based on SX1231 (SPI interface)
- +13 dBm à +20 dBm (output power up to 100 mW, power have to be set by the microcontroler at boot setup time)
- Transmission current: 50mA @ +13 dBm, 150mA @ +20dBm
- Listening current: ~30mA (active listening)
- Approx. distance 350 metres. Depend on line of sight, frequency, antenna and output power.
- Allows to create multi-point network with addressable node for each individual node
- Encryption: paquet encrypted with AES128
- Ready to use Arduino library
- Antenna: using a single wire is enough but you can solder a µFl connector.
Use the free usage ISM amateur band (ITU "Europe" license-free ISM)
The Feather 32U4 Radio avec RFM69HCW is completely assembled and tested. The 32U4 have an Arduino compatible USB bootloader (great for immediate use). Lipoly battery, USB cable, antenna, breadboard, etc are not included but we have them availables on the shop!
For each order, you will also receive a header section. You can solder them on the board if you need to use the board with a breadboard.
You will need to use and antenna with this product! Using it without antenna can damage the transmitter. Notice that a single piece of wire (solid or stranded core) would do the job.