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Revise README with updated dates and descriptions

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Updated README.md with new dates and improved descriptions.
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Kevin Thomas
2025-10-25 16:50:55 -04:00
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parent ecd135a857
commit 9f5fdf5076
1 changed files with 221 additions and 138 deletions
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RA-0x0001-GPIO-Output/README.md
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@@ -14,48 +14,58 @@ An RP2350 blink driver written entirely in Assembler.
* *
* DESCRIPTION: * DESCRIPTION:
* RP2350 Bare-Metal GPIO16 Blink, Coprocessor Version. * RP2350 Bare-Metal GPIO16 Blink, Coprocessor Version.
* Minimal bare‑metal LED blink on the RP2350 using direct coprocessor *
* BRIEF:
* Minimal bare‑metal LED blink on the RP2350 using the direct coprocessor
* (MCRR) instructions to manipulate GPIO control registers. This bypasses * (MCRR) instructions to manipulate GPIO control registers. This bypasses
* SDK abstractions and demonstrates register‑level control in assembler. * SDK abstractions and demonstrates register‑level control in assembler.
* Clocks the external crystal oscillator (XOSC) at 14.5MHz.
* *
* AUTHOR: Kevin Thomas * AUTHOR: Kevin Thomas
* CREATION DATE: October 5, 2025 * CREATION DATE: October 24, 2025
* UPDATE DATE: October 5, 2025 * UPDATE DATE: October 25, 2025
*/ */
.syntax unified // use unified assembly syntax .syntax unified // use unified assembly syntax
.cpu cortex-m33 // target Cortex-M33 core .cpu cortex-m33 // target Cortex-M33 core
.thumb // use Thumb instruction set .thumb // use Thumb instruction set
/** /**
* Memory addresses and constants. * Memory addresses and constants.
*/ */
.equ IO_BANK0_BASE, 0x40028000 // base address of IO_BANK0 .equ STACK_TOP, 0x20082000 // top of non-secure SRAM
.equ PADS_BANK0_BASE, 0x40038000 // base address of PADS_BANK0 .equ STACK_LIMIT, 0x2007A000 // stack limit (32 KB below top)
.equ SIO_BASE, 0xD0000000 // base address of SIO block .equ XOSC_BASE, 0x40048000 // base address of XOSC
.equ GPIO16_CTRL, 0x84 // io[16].ctrl offset .equ XOSC_CTRL, XOSC_BASE + 0x00 // XOSC->CTRL
.equ GPIO16_PAD, 0x44 // pads io[16] offset .equ XOSC_STATUS, XOSC_BASE + 0x04 // XOSC->STATUS
.equ GPIO16_BIT, (1<<16) // bit mask for GPIO16 .equ XOSC_STARTUP, XOSC_BASE + 0x0C // XOSC->STARTUP
.equ GPIO_OUT_SET, 0x18 // SIO->GPIO_OUT_SET offset .equ PPB_BASE, 0xE0000000 // base address of PPB
.equ GPIO_OUT_XOR, 0x28 // SIO->GPIO_OUT_XOR offset .equ CPACR, PPB_BASE + 0x0ED88 // PPB_BASE->CPACR
.equ GPIO_OE_SET, 0x38 // SIO->GPIO_OE_SET offset .equ CLOCKS_BASE, 0x40010000 // base address of CLOCKS
.equ STACK_TOP, 0x20082000 // top of non-secure SRAM .equ CLK_PERI_CTRL, CLOCKS_BASE + 0x48 // CLOCKS->CLK_PERI_CTRL
.equ STACK_LIMIT, 0x2007A000 // stack limit (32 KB below top) .equ RESETS_BASE, 0x40020000 // base address of RESETS
.equ RESETS_RESET, RESETS_BASE + 0x0 // RESETS->RESET
.equ RESETS_RESET_CLEAR, RESETS_BASE + 0x3000 // RESETS->RESET_CLEAR
.equ RESETS_RESET_DONE, RESETS_BASE + 0x8 // RESETS->RESET_DONE
.equ IO_BANK0_BASE, 0x40028000 // base address of IO_BANK0
.equ IO_BANK0_GPIO16_CTRL_OFFSET, 0x84 // IO_BANK0->GPIO16 offset
.equ PADS_BANK0_BASE, 0x40038000 // base address of PADS_BANK0
.equ PADS_BANK0_GPIO16_OFFSET, 0x44 // PADS_BANK0->GPIO16 offset
/** /**
* Initialize the .vectors section. The .vectors section contains vector * Initialize the .vectors section. The .vectors section contains vector
* table. * table and Reset_Handler.
*/ */
.section .vectors, "ax" // vector table section .section .vectors, "ax" // vector table section
.align 2 // align to 4-byte boundary .align 2 // align to 4-byte boundary
/** /**
* Vector table section. * Vector table section.
*/ */
.global _vectors // export symbol .global _vectors // export _vectors symbol
_vectors: _vectors:
.word STACK_TOP // initial stack pointer .word STACK_TOP // initial stack pointer
.word Reset_Handler + 1 // reset handler (Thumb bit set) .word Reset_Handler + 1 // reset handler (Thumb bit set)
/** /**
* @brief Reset handler for RP2350. * @brief Reset handler for RP2350.
@@ -69,12 +79,15 @@ _vectors:
* @param None * @param None
* @retval None * @retval None
*/ */
.global Reset_Handler // export Reset_Handler .global Reset_Handler // export Reset_Handler symbol
.type Reset_Handler, %function // mark as function .type Reset_Handler, %function
Reset_Handler: Reset_Handler:
BL Init_Stack // initialize MSP/PSP and limits BL Init_Stack // initialize MSP/PSP and limits
BL Enable_Coprocessor // enable CP0 in CPACR for MCRR BL Init_XOSC // initialize external crystal oscillator
B main // branch to main loop BL Enable_XOSC_Peri_Clock // enable XOSC peripheral clock
BL Init_Subsystem // initialize subsystems
BL Enable_Coprocessor // enable CP0 coprocessor
B main // branch to main loop
.size Reset_Handler, . - Reset_Handler .size Reset_Handler, . - Reset_Handler
/** /**
@@ -87,183 +100,253 @@ Reset_Handler:
*/ */
.type Init_Stack, %function .type Init_Stack, %function
Init_Stack: Init_Stack:
LDR R0, =STACK_TOP // load stack top LDR R0, =STACK_TOP // load stack top
MSR PSP, R0 // set PSP MSR PSP, R0 // set PSP
LDR R0, =STACK_LIMIT // load stack limit LDR R0, =STACK_LIMIT // load stack limit
MSR MSPLIM, R0 // set MSP limit MSR MSPLIM, R0 // set MSP limit
MSR PSPLIM, R0 // set PSP limit MSR PSPLIM, R0 // set PSP limit
LDR R0, =STACK_TOP // reload stack top LDR R0, =STACK_TOP // reload stack top
MSR MSP, R0 // set MSP MSR MSP, R0 // set MSP
BX LR // return BX LR // return
/**
* @brief Init XOSC and wait until it is ready.
*
* @details Configures and initializes the external crystal oscillator (XOSC).
* Waits for the XOSC to become stable before returning.
*
* @param None
* @retval None
*/
.type Init_XOSC, %function
Init_XOSC:
LDR R0, =XOSC_STARTUP // load XOSC_STARTUP address
LDR R1, =0x00C4 // set delay 50,000 cycles
STR R1, [R0] // store value into XOSC_STARTUP
LDR R0, =XOSC_CTRL // load XOSC_CTRL address
LDR R1, =0x00FABAA0 // set 1_15MHz, freq range, actual 14.5MHz
STR R1, [R0] // store value into XOSC_CTRL
.Init_XOSC_Wait:
LDR R0, =XOSC_STATUS // load XOSC_STATUS address
LDR R1, [R0] // read XOSC_STATUS value
TST R1, #(1<<31) // test STABLE bit
BEQ .Init_XOSC_Wait // wait until stable bit is set
BX LR // return
/**
* @brief Enable XOSC peripheral clock.
*
* @details Sets the peripheral clock to use XOSC as its AUXSRC.
*
* @param None
* @retval None
*/
.type Enable_XOSC_Peri_Clock, %function
Enable_XOSC_Peri_Clock:
LDR R0, =CLK_PERI_CTRL // load CLK_PERI_CTRL address
LDR R1, [R0] // read CLK_PERI_CTRL value
ORR R1, R1, #(1<<11) // set ENABLE bit
ORR R1, R1, #(4<<5) // set AUXSRC: XOSC_CLKSRC bit
STR R1, [R0] // store value into CLK_PERI_CTRL
BX LR // return
/**
* @brief Init subsystem.
*
* @details Initiates the various subsystems by clearing their reset bits.
*
* @param None
* @retval None
*/
.type Init_Subsystem, %function
Init_Subsystem:
.GPIO_Subsystem_Reset:
LDR R0, =RESETS_RESET // load RESETS->RESET address
LDR R1, [R0] // read RESETS->RESET value
BIC R1, R1, #(1<<6) // clear IO_BANK0 bit
STR R1, [R0] // store value into RESETS->RESET address
.GPIO_Subsystem_Reset_Wait:
LDR R0, =RESETS_RESET_DONE // load RESETS->RESET_DONE address
LDR R1, [R0] // read RESETS->RESET_DONE value
TST R1, #(1<<6) // test IO_BANK0 reset done
BEQ .GPIO_Subsystem_Reset_Wait // wait until done
BX LR // return
/** /**
* @brief Enable coprocessor access. * @brief Enable coprocessor access.
* *
* @details Grants full access to coprocessor 0 (CP0) via CPACR. * @details Grants full access to coprocessor 0 via CPACR.
* *
* @param None * @param None
* @retval None * @retval None
*/ */
.type Enable_Coprocessor , %function .type Enable_Coprocessor , %function
Enable_Coprocessor: Enable_Coprocessor:
LDR R0, =0xE000ED88 // CPACR address LDR R0, =CPACR // load CPACR address
LDR R1, [R0] // read CPACR LDR R1, [R0] // read CPACR value
ORR R1, R1, #0x3 // set CP0 full access ORR R1, R1, #(1<<1) // set CP0: Controls access priv coproc 0 bit
STR R1, [R0] // write CPACR ORR R1, R1, #(1<<0) // set CP0: Controls access priv coproc 0 bit
DSB // data sync barrier STR R1, [R0] // store value into CPACR
ISB // instruction sync barrier DSB // data sync barrier
BX LR // return ISB // instruction sync barrier
BX LR // return
/** /**
* Initialize the .text section. * Initialize the .text section.
* The .text section contains executable code. * The .text section contains executable code.
*/ */
.section .text // code section .section .text // code section
.align 2 // align to 4-byte boundary .align 2 // align to 4-byte boundary
/** /**
* @brief Main application entry point. * @brief Main application entry point.
* *
* @details Implements the infinite blink loop: * @details Implements the infinite blink loop.
* - Set GPIO16 high
* - Delay ~500 ms
* - Set GPIO16 low
* - Delay ~500 ms
* - Repeat forever
* *
* @param None * @param None
* @retval None * @retval None
*/ */
.global main // export main .global main // export main
.type main, %function // mark as function .type main, %function // mark as function
main: main:
.Push_Registers: .Push_Registers:
PUSH {R4-R12, LR} // push registers R4-R12, LR to the stack PUSH {R4-R12, LR} // push registers R4-R12, LR to the stack
.GPIO16_Config: .GPIO16_Config:
BL GPIO16_Config // configure pads and FUNCSEL for GPIO16 LDR R0, =PADS_BANK0_GPIO16_OFFSET // load PADS_BANK0_GPIO16_OFFSET
LDR R1, =IO_BANK0_GPIO16_CTRL_OFFSET // load IO_BANK0_GPIO16_CTRL_OFFSET
LDR R2, =16 // load GPIO number
BL GPIO_Config // call GPIO_Config
.Loop: .Loop:
BL GPIO16_Set // set GPIO16 high LDR R0, =16 // load GPIO number
BL Delay_500ms // ~500 ms delay BL GPIO_Set // call GPIO_Set
BL GPIO16_Clear // set GPIO16 low LDR R0, =500 // 500ms
BL Delay_500ms // ~500 ms delay BL Delay_MS // call Delay_MS
B Loop // loop forever LDR R0, =16 // load GPIO number
BL GPIO_Clear // call GPIO_Clear
LDR R0, =500 // 500ms
BL Delay_MS // call Delay_MS
B .Loop // loop forever
.Pop_Registers: .Pop_Registers:
POP {R4-R12, LR} // pop registers R4-R12, LR from the stack POP {R4-R12, LR} // pop registers R4-R12, LR from the stack
BX LR // return to caller BX LR // return to caller
/** /**
* @brief Configure GPIO16 for SIO control. * @brief Configure GPIO.
* *
* @details Sets pad control (IE, OD, ISO) and FUNCSEL = 5 (SIO). Enables OE. * @details Configures a GPIO pin's pad control and function select.
* *
* @param None * @param R0 - PAD_OFFSET
* @param R1 - CTRL_OFFSET
* @param R2 - GPIO
* @retval None * @retval None
*/ */
.type GPIO16_Config, %function .type GPIO_Config, %function
GPIO16_Config: GPIO_Config:
.GPIO16_Config_Push_Registers: .GPIO_Config_Push_Registers:
PUSH {R4-R12, LR} // push registers R4-R12, LR to the stack PUSH {R4-R12, LR} // push registers R4-R12, LR to the stack
.GPIO16_Config_Modify_Pad: .GPIO_Config_Modify_Pad:
LDR R3, =PADS_BANK0_BASE + GPIO16_PAD // pad control address LDR R4, =PADS_BANK0_BASE // load PADS_BANK0_BASE address
LDR R2, [R3] // read pad config ADD R4, R4, R0 // PADS_BANK0_BASE + PAD_OFFSET
BIC R2, R2, #0x80 // clear OD LDR R5, [R4] // read PAD_OFFSET value
ORR R2, R2, #0x40 // set IE BIC R5, R5, #(1<<7) // clear OD bit
BIC R2, R2, #0x100 // clear ISO ORR R5, R5, #(1<<6) // set IE bit
STR R2, [R3] // write pad config BIC R5, R5, #(1<<8) // clear ISO bit
.GPIO16_Config_Modify_IO: STR R5, [R4] // store value into PAD_OFFSET
LDR R3, =IO_BANK0_BASE + GPIO16_CTRL // IO control address .GPIO_Config_Modify_CTRL:
LDR R2, [R3] // read IO config LDR R4, =IO_BANK0_BASE // load IO_BANK0 base
BIC R2, R2, #0x1F // clear FUNCSEL ADD R4, R4, R1 // IO_BANK0_BASE + CTRL_OFFSET
ORR R2, R2, #5 // set FUNCSEL=5 LDR R5, [R4] // read CTRL_OFFSET value
STR R2, [R3] // write IO config BIC R5, R5, #0x1F // clear FUNCSEL
.GPIO16_Config_Enable_OE: ORR R5, R5, #0x05 // set FUNCSEL 0x05->SIO_0
MOVS R4, #16 // GPIO number STR R5, [R4] // store value into CTRL_OFFSET
MOVS R5, #1 // enable output .GPIO_Config_Enable_OE:
MCRR p0, #4, R4, R5, c4 // gpioc_bit_oe_put(16, 1) LDR R4, =1 // enable output
.GPIO16_Config_Pop_Registers: MCRR P0, #4, R2, R4, C4 // gpioc_bit_oe_put(GPIO, 1)
POP {R4-R12, LR} // pop registers R4-R12, LR from the stack .GPIO_Config_Pop_Registers:
BX LR // return POP {R4-R12, LR} // pop registers R4-R12, LR from the stack
BX LR // return
/** /**
* @brief Set GPIO16 high. * @brief GPIO set.
* *
* @details Drives GPIO16 output = 1 via coprocessor MCRR. * @details Drives GPIO output high via coprocessor.
* *
* @param None * @param R0 - GPIO
* @retval None * @retval None
*/ */
.type GPIO16_Set, %function .type GPIO_Set, %function
GPIO16_Set: GPIO_Set:
.GPIO16_Set_Push_Registers: .GPIO_Set_Push_Registers:
PUSH {R4-R12, LR} // push registers R4-R12, LR to the stack PUSH {R4-R12, LR} // push registers R4-R12, LR to the stack
.GPIO16_Set_Load_Operands: .GPIO_Set_Execute:
MOVS R4, #16 // GPIO number LDR R4, =1 // enable output
MOVS R5, #1 // logic high MCRR P0, #4, R0, R4, C0 // gpioc_bit_out_put(GPIO, 1)
.GPIO16_Set_Execute: .GPIO_Set_Pop_Registers:
MCRR p0, #4, R4, R5, c0 // gpioc_bit_out_put(16, 1) POP {R4-R12, LR} // pop registers R4-R12, LR from the stack
.GPIO16_Set_Pop_Registers: BX LR // return
POP {R4-R12, LR} // pop registers R4-R12, LR from the stack
BX LR // return to caller
/** /**
* @brief Clear GPIO16 (set low). * @brief GPIO clear.
* *
* @details Drives GPIO16 output = 0 via coprocessor MCRR. * @details Drives GPIO output high via coprocessor.
* *
* @param None * @param R0 - GPIO
* @retval None * @retval None
*/ */
.type GPIO16_Clear, %function .type GPIO_Clear, %function
GPIO16_Clear: GPIO_Clear:
.GPIO16_Clear_Push_Registers: .GPIO_Clear_Push_Registers:
PUSH {R4-R12, LR} // push registers R4-R12, LR to the stack PUSH {R4-R12, LR} // push registers R4-R12, LR to the stack
.GPIO16_Clear_Load_Operands: .GPIO_Clear_Execute:
MOVS R4, #16 // GPIO number LDR R4, =0 // disable output
MOVS R5, #0 // logic low MCRR P0, #4, R0, R4, C0 // gpioc_bit_out_put(GPIO, 1)
.GPIO16_Clear_Execute: .GPIO_Clear_Pop_Registers:
MCRR p0, #4, R4, R5, c0 // gpioc_bit_out_put(16, 0) POP {R4-R12, LR} // pop registers R4-R12, LR from the stack
.GPIO16_Clear_Pop_Registers: BX LR // return
POP {R4-R12, LR} // pop registers R4-R12, LR from the stack
BX LR // return to caller
/** /**
* @brief Busy‑wait Delay_500ms loop. * @brief Delay_MS.
* *
* @details Consumes ~2,000,000 cycles to approximate ~500 ms at boot clock. * @details Delays for R0 milliseconds. Conversion: loop_count = ms * 3600
* based on a 14.5MHz clock.
* *
* @param None * @param R0 - milliseconds
* @retval None * @retval None
*/ */
.type Delay_500ms, %function .type Delay_MS, %function
Delay_500ms: Delay_MS:
.Delay_500ms_Push_Registers: .Delay_MS_Push_Registers:
PUSH {R4-R12, LR} // push registers R4-R12, LR to the stack PUSH {R4-R12, LR} // push registers R4-R12, LR to the stack
.Delay_500ms_Setup: .Delay_MS_Check:
LDR R2, =2000000 // loop count (~500 ms) CMP R0, #0 // if MS is not valid, return
.Delay_500ms_Loop: BLE .Delay_MS_Done // branch if less or equal to 0
SUBS R2, R2, #1 // decrement counter .Delay_MS_Setup:
BNE .Delay_500ms_Loop // branch until zero LDR R4, =3600 // loops per MS based on 14.5MHz clock
.Delay_500ms_Pop_Registers: MUL R5, R0, R4 // MS * 3600
POP {R4-R12, LR} // pop registers R4-R12, LR from the stack .Delay_MS_Loop:
BX LR // return to caller SUBS R5, R5, #1 // decrement counter
BNE .Delay_MS_Loop // branch until zero
.Delay_MS_Done:
POP {R4-R12, LR} // pop registers R4-R12, LR from the stack
BX LR // return
/** /**
* Test data and constants. * Test data and constants.
* The .rodata section is used for constants and static data. * The .rodata section is used for constants and static data.
*/ */
.section .rodata // read-only data section .section .rodata // read-only data section
/** /**
* Initialized global data. * Initialized global data.
* The .data section is used for initialized global or static variables. * The .data section is used for initialized global or static variables.
*/ */
.section .data // data section .section .data // data section
/** /**
* Uninitialized global data. * Uninitialized global data.
* The .bss section is used for uninitialized global or static variables. * The .bss section is used for uninitialized global or static variables.
*/ */
.section .bss // BSS section .section .bss // BSS section
``` ```
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