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78 lines
2.7 KiB
78 lines
2.7 KiB
# AVR C Boilerplate
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This is a basic boilerplate for programming AVRs in C.
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The project aims to make programming Arduinos in C fun by
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providing support for basic functionality like GPIO and USART,
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so you can start developing without having the datasheet open
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all the time.
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It is intended for **ATmega328P** (the chip in Arduinos),
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but can be easily adapted to other parts.
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## Requirements
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Before you can start coding, you need to install a few software packages:
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- `avrdude` - the flash tool
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- `avr-gcc` - compiler
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- `avr-libc` - libc implementation for AVR
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- `avr-binutils` - utils for manipulating AVR binaries
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- `make` - to run the Makefile
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There's a good chance you already have `make`, the rest should be in your
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distribution's repos.
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If you're on Arch:
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```
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# pacman -S base-devel avr-gcc avr-binutils avr-libc avrdude
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```
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If you're on Mac, you should be able to pull the stuff with *brew*.
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## Getting started
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The provided `main.c` is a good starting point - it contains some simple demo code.
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You can compile it with `make` and flash with `make flash`.
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### Before you can flash
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First, check that the `avrdude` options in the file are correct for your system - especially
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the device and speed.
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```ini
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# AVRDUDE settings
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PROG_BAUD = 57600
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PROG_DEV = /dev/ttyUSB0
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PROG_TYPE = arduino
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# Build the final AVRDUDE arguments
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PROG_ARGS = -c $(PROG_TYPE) -p $(MCU) -b $(PROG_BAUD) -P $(PROG_DEV)
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```
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- Adjust `PROG_DEV` to the device your board is connected to. On Linux it's usually
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`/dev/ttyUSB0`, but it can also be `/dev/ttyACM0` or something else. On Mac, it'll be
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`/dev/cu.xxx`. On Windows it's some `COMx`.<br>
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Linux and Mac users can use `ls /dev` to see their devices. Windows users will find
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this in their Device Manager.
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- You may also adjust the baudrate (`PROG_BAUD`). Some boards need `115200`.
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**TIP:** You can look what the Arduino IDE is using - it's running avrdude too.
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### Adding new files
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- If you *add a new C file* to the project, add an entry for it's `.o` (object file,
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created by the compiler before linking) to the `OBJS` list in the Makefile.
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- Similarly, if you *add a new folder with header files*, add it to `INCL_DIRS`.
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- In case you need `printf` (or `printf` with floats), enable the appropriate LD_FLAGS
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in the Makefile (it's well commented). Code size will - obviously - grow quite a bit.
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## Notes
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- The **Arduino UNO** bootloader has a quirk where `Double Speed Asynchronous Mode` for USART
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is enabled by default, so if you set your baud rate to 9600, you'd really get 19200.<br>
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We correct this in the `usart_init()` function to keep things consistent and to avoid
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confusion.<br>
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*If you wish to turn this on* however, you can do so by using `usart_set_2x(true)`.
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