AVR Libc
- Introduction
- General information about this library
- Supported Devices
- avr-libc License
Toolchain Overview
- Introduction
- FSF and GNU
- GCC
- GNU Binutils
- avr-libc
- Building Software
- AVRDUDE
- GDB / Insight / DDD
- AVaRICE
- SimulAVR
- Utilities
- Toolchain Distributions (Distros)
- Open Source
Memory Areas and Using malloc()
- Introduction
- Internal vs. external RAM
- Tunables for malloc()
- Implementation details
Memory Sections
- The .text Section
- The .data Section
- The .bss Section
- The .eeprom Section
- The .noinit Section
- The .initN Sections
- The .finiN Sections
- Using Sections in Assembler Code
- Using Sections in C Code
Data in Program Space
- Introduction
- const Keyword
- Data
- Strings
- Caveats
avr-libc and assembler programs
- Introduction
- Invoking the compiler
- Example program
- Pseudo-ops and operators
Inline Assembler Cookbook
- GCC asm Statement
- Assembler Code
- Input and Output Operands
- Clobbers
- Assembler Macros
- C Stub Functions
- C Names Used in Assembler Code
- Links
How to Build a Library
- Introduction
- How the Linker Works
- How to Design a Library
- Creating a Library
- Using a Library
Benchmarks
- Some libc functions
- Math functions
Porting From IAR to AVR GCC
- Introduction
- Registers
- Interrupt Service Routines (ISRs)
- Intrinsic Routines
- Flash Variables
- Non-Returning main()
- Locking Registers
Frequently Asked Questions
- My program doesn't recognize a variable updated within an interrupt routine
- I get "undefined reference to..." for functions like "sin()"
- How to permanently bind a variable to a register?
- How to modify MCUCR or WDTCR early?
- What is all this _BV() stuff about?
- Can I use C++ on the AVR?
- Shouldn't I initialize all my variables?
- Why do some 16-bit timer registers sometimes get trashed?
- How do I use a #define'd constant in an asm statement?
- Why does the PC randomly jump around when single-stepping through my program in avr-gdb?
- How do I trace an assembler file in avr-gdb?
- How do I pass an IO port as a parameter to a function?
- What registers are used by the C compiler?
- How do I put an array of strings completely in ROM?
- How to use external RAM?
- Which -O flag to use?
- How do I relocate code to a fixed address?
- My UART is generating nonsense! My ATmega128 keeps crashing! Port F is completely broken!
- Why do all my "foo...bar" strings eat up the SRAM?
- Why does the compiler compile an 8-bit operation that uses bitwise operators into a 16-bit operation in assembly?
- How to detect RAM memory and variable overlap problems?
- Is it really impossible to program the ATtinyXX in C?
- What is this "clock skew detected" message?
- Why are (many) interrupt flags cleared by writing a logical 1?
- Why have "programmed" fuses the bit value 0?
- Which AVR-specific assembler operators are available?
- Why are interrupts re-enabled in the middle of writing the stack pointer?
- Why are there five different linker scripts?
- How to add a raw binary image to linker output?
- How do I perform a software reset of the AVR?
- I am using floating point math. Why is the compiled code so big? Why does my code not work?
- What pitfalls exist when writing reentrant code?
- Why are some addresses of the EEPROM corrupted (usually address zero)?
- Why is my baud rate wrong?
Building and Installing the GNU Tool Chain
Using the GNU tools
Using the avrdude program
Release Numbering and Methodology
Acknowledgments
Todo List
Deprecated List
Library Reference
- : Allocate stack space
  - alloca
- : Diagnostics
  - assert
- : Character Operations
  - Conversion
- : System Errors
  - errno Variable
- : Integer Type conversions
- : Mathematics
  - Constants
  - Miscellaneous
    - fabs
    - fdim
    - fma
    - fmin
    - fmax
    - fmod
    - modf
  - Inspect
  - Exponential
    - exp
    - ldexp
    - pow
    - log
    - log10
    - square
    - sqrt
    - cbrt
  - Trigonometric
    - sin
    - cos
    - tan
    - asin
    - acos
    - atan
    - atan2
    - hypot
  - Hyperbolic
  - Rounding
    - ceil
    - floor
    - round
    - lround
    - rint
    - lrint
    - trunc
- : Non-local goto
  - setjmp
  - longjmp
- : Standard Integer Types
- : Standard IO facilities
  - Types, Constants, and Globals
  - Stream Setup
  - Open, Close, Status
  - Stream Input
  - Formatted Input
  - Stream Output
  - Formatted Output
- : General utilities
  - Memory allocation
  - Number-String conversion
  - Integer math
  - Other functions
- : Strings
  - Search Character(s)
  - String Compare
    - strcmp, strcasecmp, strncmp, strncasecmp
    - strstr, strcasestr
  - String Copy
  - Inplace Modification
  - Memory Functions
  - Others
    - __ATTR_PURE__
    - _FFS, ffs, ffsl, ffsll(x)
- : Bootloader Support Utilities
- : EEPROM handling
  - Read
  - Write
  - Update
- : Fuse Support
  - Macros
- : Lockbit Support
  - Macros
- : Interrupts
  - ISR: Declare Interrupt Service Routine
  - EMPTY_INTERRUPT: Declare empty ISR
  - cli(), sei(): Switch Interrupt Flag
- : AVR device-specific IO definitions
- : Program Space Utilities
- : Power Reduction Management
  - PRR: Power Reduction Register
  - CLKPR: Clock Prescaler
- : Special function registers
  - Additional notes from
- : Signature Support
- : Power Management and Sleep Modes
  - sleep_enable
  - sleep_disable
  - sleep_cpu
- : avr-libc version macros
- : Watchdog timer handling
  - wdt_enable
  - wdt_disable
  - wdt_reset
- Atomically and Non-Atomically Executed Code Blocks
- : CRC Computations
Demo Projects
- A simple project
- A more sophisticated project
- Using the standard IO facilities
- Example using the two-wire interface (TWI)
- Combining C and assembly source files