FC3000 >> Assembly

UART

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參考資料：
1. pdf
2. lichee
3. mangopi_r
4. allwinner

UART0腳位位於PE0、PE1


位址


暫存器


Baudrate計算方式

PLL = 24MHz*N*K/M

0x80041800:
  K = 1
  M = 1
  N = 24

PLL_PERIPH = 24MHz*25 = 600MHz
AHB_CLK = PLL_PERIPH/(AHB_PRE_DIV*AHB_CLK_DIV_RATIO) = 600MHz/(3*1) = 200MHz
APB_CLK = AHB_CLK/APB_CLK_RATIO = 200MHz/2 = 100MHz

0x00003180:
  AHB_PRE_DIV = 3
  APB_CLK_RATIO = 2
  AHB_CLK_DIV_RATIO = 1

Baudrate = APB_CLK/(16*divisor) = 100MHz/(16*54) = 115741 ~= 115200

main.s

  .global _start
   
  .equ CCU_BASE,   0x01c20000
  .equ GPIO_BASE,  0x01c20800
  .equ UART0_BASE, 0x01c25000
  
  .equ PLL_PERIPH_CTRL_REG,   0x0028
  .equ AHB_APB_HCLKC_CFG_REG, 0x0054
  .equ BUS_CLK_GATING_REG2,   0x0068
  .equ BUS_SOFT_RST_REG2,     0x02d0
 
  .equ PE,   (0x24 * 4) 
  .equ CFG0, 0x00
  .equ DATA, 0x10
  .equ RBR,  0x0000
  .equ DLL,  0x0000
  .equ DLH,  0x0004
  .equ IER,  0x0004
  .equ IIR,  0x0008
  .equ LCR,  0x000c
  .equ MCR,  0x0010
  .equ USR,  0x007c
  
  .arm
  .text
_start:
  .long 0xea000016
  .byte 'e', 'G', 'O', 'N', '.', 'B', 'T', '0'
  .long 0, __spl_size
  .byte 'S', 'P', 'L', 2
  .long 0, 0
  .long 0, 0, 0, 0, 0, 0, 0, 0
  .long 0, 0, 0, 0, 0, 0, 0, 0
  
_vector:
  b reset
  b .
  b .
  b .
  b .
  b .
  b .
  b .
  
reset:
  ldr r0, =CCU_BASE
  ldr r1, =0x80041800
  str r1, [r0, #PLL_PERIPH_CTRL_REG]
  ldr r1, =0x00003180
  str r1, [r0, #AHB_APB_HCLKC_CFG_REG]
 
  ldr r0, =GPIO_BASE
  ldr r1, =0x55
  str r1, [r0, #(PE + CFG0)]
 
  ldr r0, =CCU_BASE
  ldr r1, =(1 << 20)
  str r1, [r0, #BUS_CLK_GATING_REG2]
  str r1, [r0, #BUS_SOFT_RST_REG2]
 
  ldr r0, =UART0_BASE
  ldr r1, =0x00
  str r1, [r0, #IER]
  ldr r1, =0xf7
  str r1, [r0, #IIR]
  ldr r1, =0x00
  str r1, [r0, #MCR]
  ldr r1, [r0, #LCR]
  orr r1, #(1 << 7)
  str r1, [r0, #LCR]
  ldr r1, =54
  str r1, [r0, #DLL]
  ldr r1, =0x00
  str r1, [r0, #DLH]
  ldr r1, [r0, #LCR]
  bic r1, #(1 << 7)
  str r1, [r0, #LCR]
  ldr r1, [r0, #LCR]
  bic r1, #0x1f
  orr r1, #0x03
  str r1, [r0, #LCR]
  
  ldr r0, =UART0_BASE
  ldr r2, =hello
1:
  ldr r1, [r0, #USR]
  tst r1, #(1 << 1)
  beq 1b
  ldrb r1, [r2]
  strb r1, [r0, #RBR]
  add r2, #1
  cmp r1, #0
  bne 1b
  
main:
  b main
  
  .align
hello: .asciz "123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890"
  .end

P.S. F1C100S從MicroSD啟動時，程式必須大於512 Bytes才可以啟動，小於等於512 Bytes不行，這也是為何司徒要塞這麼多Dummy資料的原因

Baudrate: 115200bps

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