kasparsd / passive-sense

Passive Sense

One module that can:

• Transmit and receive sensor data over RFM69 and RS-485.
• Connect RFM69 to Raspberry PI via SPI0.

Components

• ATTiny84 microcontroller
• RFM69 radio transceiver
• MAX485/MAX1487 RS-485 transceiver

Connections

RFM69 transceiver to ATTiny84 via USI-SPI since it doesn't have hardware SPI:

• MOSI to PA5 (USI-DO, instead of PA6)
• MISO to PA6 (USI-DI)
• SCK to PA4 (USI-SCK)
• NSS to PB2
• DIO0 to PA7

RFM69 transceiver to Raspberry PI SPI0 header:

• VCC to 3.3V (GPIO9)
• MOSI to MOSI (GPIO10)
• MISO to MISO (GPIO9)
• SCK to CLK (GPIO11)
• NSS to CE (GPIO8)
• DIO0 to GPIO25

MAX485 to ATTiny84 using software serial:

• RO to PA2 as RX
• DI to PA1 as TX
• DE and RE to PA3

Programming

Via 6-pin ISP connector.

Layout and PCB

• Schematics (PDF)
• PCB (PDF)

See easyeda.com/kasparsd/tiny-sensor-433mhz-rs485.

passive-sense's Issues

Prototypes

Here are the prototypes in Arduino code in case anyone finds them valuable:

• mysensor-raw.zip
• mysensors-first.zip

Note that you'll need to install the necessary Arduino libraries to get this to work.