This is a simple MYSensors (https://www.mysensors.org/) board, with a standard NRF24L01+ with DIL header and only 1 resistor and 3 capacitors. I decided to place the NRF24L01+ in this orientation to shorten the board when placing it in small housings. The board is designed to use Over The Air (OTA) uploading for sketches.

The board itself is a double-sided PCB, manufactored at allpcb.com (http://allpcb.com/) for a very low prize. Shipping from China to Germany took 2 days with TNT, so I will definitively order more boards at allpcb.com. Design files (Gerber) available in the files tab.

The PCB is tested and works well, but surely I cannot give any kind of guarantee for anything related to the board. There is second similar board with the CE and CSN pin of the NRF24L01+ connected to the ATMega328p pins 8 and 9 in order to use SPI also for other devices in parallel (pictures of boths variants included). In this case no OTA for now, I am still working on adapting the bootloader for this pin combination.

The board is quite simple, has most of the ATMega328p pins available for adding multiple sensors very easily. The I2C pins (VCC - GND - SDA - SCL) are accessable at one side of the board in order to solder a HTU21D/SHT21 (temp/humidity) sensor directly to the board without any cables.

I put some additional solderpads for VCC and GND additionally next to some Dx pins (e.g. D2, D5) to easily solder sensors, actors or LEDs next to them.

The board has no explicit connectors for ISP nor FTDI because I only use OTA and I wanted to keep the PCB very small (49 x 19 mm) and simple. So I use the OTA-bootloader that comes with MYSController by tekka (https://github.com/mysensors/MySensorsBootloaderRF24) with 8MHz internal oscillator and 2 AA batteries. RX/TX pins have no extra solderpads on the board to connect pin headers for FTDI.

My boards like this usually keep running for several months with 2 AA batteries and a reporting interval of every 10 minutes using e.g. smartSleep() from MySensors.

Have fun

I use this boards.txt for flashing the bootloader from MySensorsBootloaderRF24 using usbasp before uploading the sketches via OTA and MYSController.

MYSBL.name=ATmega328 with MYSBootloader 1.3.0 8 MHz (2018/01)
MYSBL.upload.tool=arduino:avrdude
MYSBL.upload.protocol=arduino
MYSBL.upload.maximum_size=30720
MYSBL.upload.maximum_data_size=2048
MYSBL.bootloader.tool=arduino:avrdude
MYSBL.bootloader.unlock_bits=0x3F
MYSBL.bootloader.lock_bits=0x0F
MYSBL.build.mcu=atmega328p
MYSBL.build.board=AVR_PRO
MYSBL.build.core=arduino:arduino
MYSBL.build.variant=arduino:standard
MYSBL.f_cpu=8000000L
MYSBL.upload.speed=38400
MYSBL.bootloader.low_fuses=0xE2
MYSBL.bootloader.high_fuses=0xD2
MYSBL.bootloader.extended_fuses=0x06
MYSBL.build.f_cpu=8000000L
MYSBL.bootloader.file=MYSBootloader_8MHz.hex