104 lines
2.5 KiB
Markdown
104 lines
2.5 KiB
Markdown
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# ATTiny85 Hello World
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Blinking an LED using an ATTiny85 programmed with `avr-gcc` and `avrdude` on Mac OS X.
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## Mac OS X AVR toolchain install
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Using Homebrew, tap [larsimmisch's homebrew-avr repository](https://github.com/larsimmisch/homebrew-avr):
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```
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brew tap larsimmisch/avr
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brew install avr-libc
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```
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## Build steps
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1. Compile with `avr-gcc`
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2. Prepare the hex file with `avr-objcopy`
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3. Flash the hex with `avrdude`
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```
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avr-gcc -Wall -Os -DF_CPU=1000000 -mmcu=attiny85 -o hello.o hello.c
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avr-objcopy -j .text -j .data -O ihex hello.o hello.hex
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avrdude -c usbtiny -p t85 -U flash:w:hello.hex:i
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```
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`F_CPU` must be defined at the `avr-gcc` command line or above the `#include <util/delay.h>`
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so the delay library knows the microcontroller's clock speed.
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## Breadboard configuration
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Wire the ISP-6 cable from the USBTinyISP to the breadboarded ATTiny85 using jumpers.
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### ISP-6 pinout
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Looking at the ISP-6 *cable* with the connector key at the bottom, the pins are numbered
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like this:
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```
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+-----------+
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|(6) (4) (2)|
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|(5) (3) (1)|
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+-----------+
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```
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1. MISO
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2. Vcc
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3. SCK
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4. MOSI
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5. Reset
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6. Ground
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(See also [this photo](http://www.ics.uci.edu/~givargis/courses/cs145/resources/avrisp.png))
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### ATTiny85 pintout
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The ATTiny85's pins are:
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```
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(8) (7) (6) (5)
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+---------------+
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| o |
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+---------------+
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(1) (2) (3) (4)
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```
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1. PB5 (Reset)
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2. PB3
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3. PB4
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4. Ground
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5. PB0 (MOSI)
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6. PB1 (MISO)
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7. PB2 (SCK)
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8. Vcc
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### Programming jumpers
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Connect the ISP and the ATTiny85 together on the Ground, MISO (Master In, Slave Out),
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MOSI (Master Out, Slave In), SCK (Serial ClocK), Reset, and Vcc pins:
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- ISP-6 pin 1–ATTiny85 pin 6 (MISO)
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- ISP-6 pin 2–ATTiny85 pin 8 (Vcc)
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- ISP-6 pin 3–ATTiny85 pin 7 (SCK)
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- ISP-6 pin 4–ATTiny85 pin 5 (MOSI)
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- ISP-6 pin 5–ATTiny85 pin 1 (Reset)
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- ISP-6 pin 6–ATTiny85 pin 4 (Ground)
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N.B. The ATTiny's pins 2 and 3 are unconnected.
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### LED circuit
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Power the LED with a transistor and a series resistor, switching the transistor using a resistor
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from the ATTiny's pin 2 to the transistor's base.
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## References
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- [Honey, I Shrunk the Arduino](http://www.instructables.com/id/Honey-I-Shrunk-the-Arduino-Moving-from-Arduino-t/?ALLSTEPS)
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- [ATTiny85 and ISP-6 pinouts](http://fabienroyer.wordpress.com/2010/12/12/build-a-cheap-flexible-avr-microcontroller-programming-target-board/)
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- [ATTiny85 pinout](http://teslaui.files.wordpress.com/2012/11/attiny85_pins.png)
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- [Atmel's in-system programming documentation](http://www.atmel.com/Images/doc0943.pdf)
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