ARM GNU Assembly Programming From Ground Up™

Explore the Arm design philosophy and the RISC architecture, noting Arm as a Cambridge design firm licensing architecture, not hardware, with single-cycle instructions, pipelines, and general-purpose registers.

Explore the ARM, Thumb, and Thumb-2 instruction sets, comparing 32-bit ARM instructions with 16-bit Thumb. Learn how Thumb-2 blends 16- and 32-bit forms and why some cores run only Thumb-2.

Learn how directives, or pseudo-ops, guide the assembly process, not execute code, using .thumb, .syntax, .cpu, .section, .global, .equ, .end, .space, .align, .req, .byte, .hword, .word, and .quad.

Use the .req directive to rename registers with symbolic names like val1, val2, and sum; move values into r1 and r2 and add to store the result in r3.

Learn how load-store instructions move data between memory and registers in ARM, using LDR/STR variants for byte, halfword, and 32-bit data, with base-plus-offset addressing and left shifts.

Explain endianness and how ARM supports little and big endian through hardware and software, with little endian as default and big endian usable for certain applications like network traffic.

Export from assembly to c by creating main.c and function.s, exposing number_func with .globl, and calling it from main to return 121 in r0.

Master logical shifts in arm gnu assembly, including left and right shifts and their relation to multiplying or dividing by 2^n; arithmetic shifts preserve the sign bit.

Discover how to multiply by constants on ARM using a barrel shifter with add/sub, generating powers of two and simple combinations in low-power applications without a multiplier array.

Finds the minimum signed value in an array of nine elements by iterating with signed byte loads, updating the current min, and looping until the counter reaches zero.

Explore the push and pop instructions and their shared syntax, with an optional condition code and a comma-separated register list, and note how both exclude the program counter.

Develop a gpio driver in assembly by studying microcontroller memory maps and register configurations, using stm32f411 data sheets, reference manual, and the nucleo user guide to locate and configure pins.

Implement an input driver in ARM GNU assembly by initializing GPIO, configuring PA5 as output and PC13 as input, reading IDR, and toggling PA5 via BSRR from the active-low button.

Implement the adc read function by starting conversion with SWSTART and waiting for the EOC flag. Read the result from the adc data register and return it in r0.