ATTiny85-based Green Card

ATTiny85-based Green Card

Goals

Simplest possible Bluetooth 4 sensor board
Easy to program
Fully open source and DIY-able
Actually low-power. Should work a long time on a coin-cell battery (months). No extra LEDs, no extra components on board that can drain current

Implementation

nRF8001

Required pins:

ACI Data (the same as a normal SPI interface); MOSI, MISO, SCK.
ACI Request Pin: REQn. Input pin signalling that the controller has data to send. Active low.
ACI Ready Pin: RDYn. Output pin signalling that the radio has data to send. Active low.
Power, VCC and GND.

In total: 5 pins + 2 power pins.

ATTIny85

Olimex's ATTiny 85 Boards

These all have the same pins available:

0: PB0/MOSI/DI/SDA/AIN0/OC0A/#OC1A/AREF/PCINT0
1: PB1/MISO/DO/AIN1/OC0B/OC1A/PCINT1
2: PB2/SCK/USCK/SCL/ADC1/T0/INT0/PCINT2
3: PB3/PCINT3/XTAL1/CLKI/#OC1B/ADC3. Connected to USB port.
4: PB4/PCINT4/XTAL2/CLKO/OC1B/ADC2. Connected to USB port.
5: PB5/PCINT5/#RESET/ADC0/DW. Connected to reset button.

Possible connections to nRF8001 => ATTiny85:

MOSI => 0
MISO => 1
SCL => 2
REQn => 3
RDYn => 4. This will use the interrupt feature of PCINT4.

This leaves pin 5 which can be used as an analog signal or as a chip select for another chip on the SPI bus.

OLIMEXINO-85BC

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Price: €7.
3.3V Voltage regulator and integrated Li-Po charger.
Pin header at one end of the board, USB and battery connectors at the other end.
Two leds, power and status.
Product page

OLIMEXINO-85S

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Price: €5.
No voltage regulator.
Two leds, power and status.
Very small.
Product page

OLIMEXINO-85-KIT

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Price: €4. €6 for assembled version.
Build it yourself kit.
Two leds, power and status.
Pin header at one end of the board, USB-B connector at the other end.
Product page