暫存器
TWI速度計算
參考資料：
http://nano.lichee.pro/
https://mangopi.org/mangopi_r
I2C0腳位
| I2C0_SCK | PD12 |
|---|---|
| I2C0_SDA | PD0 |
暫存器
TWI速度計算
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
CLK_N = 3
CLK_M = 2
TWI = 100MHz/(2^CLK_N)*(CLK_M+1)*10 = 100MHz/240 = 416KHz ~= 400KHz
傳送步驟：
1. 設定I2C_START(M_STA)
2. 寫入I2C_DATA(TWI_DATA_REG)
3. 清除INTF(INT_FLAG)
4. 設定I2C_STOP(M_STP)
5. 清除INTF(INT_FLAG)
6. 等待I2C BUS閒置(STAT=0xf8)
Code Status
0x00: Bus error 0x08: START condition transmitted 0x10: Repeated START condition transmitted 0x18: Address + Write bit transmitted, ACK received 0x20: Address + Write bit transmitted, ACK not received 0x28: Data byte transmitted in master mode, ACK received 0x30: Data byte transmitted in master mode, ACK not received 0x38: Arbitration lost in address or data byte 0x40: Address + Read bit transmitted, ACK received 0x48: Address + Read bit transmitted, ACK not received 0x50: Data byte received in master mode, ACK transmitted 0x58: Data byte received in master mode, not ACK transmitted 0x60: Slave address + Write bit received, ACK transmitted 0x68: Arbitration lost in address as master, slave address + Write bit received, ACK transmitted 0x70: General Call address received, ACK transmitted 0x78: Arbitration lost in address as master, General Call address received, ACK transmitted 0x80: Data byte received after slave address received, ACK transmitted 0x88: Data byte received after slave address received, not ACK transmitted 0x90: Data byte received after General Call received, ACK transmitted 0x98: Data byte received after General Call received, not ACK transmitted 0xA0: STOP or repeated START condition received in slave mode 0xA8: Slave address + Read bit received, ACK transmitted 0xB0: Arbitration lost in address as master, slave address + Read bit received, ACK transmitted 0xB8: Data byte transmitted in slave mode, ACK received 0xC0: Data byte transmitted in slave mode, ACK not received 0xC8: Last byte transmitted in slave mode, ACK received 0xD0: Second Address byte + Write bit transmitted, ACK received 0xD8: Second Address byte + Write bit transmitted, ACK not received 0xF8: No relevant status information, INT_FLAG=0
main.s
.global _start
.equiv CCU_BASE, 0x01c20000
.equiv GPIO_BASE, 0x01c20800
.equiv TWI0_BASE, 0x01c27000
.equiv PLL_PERIPH_CTRL_REG, 0x0028
.equiv AHB_APB_HCLKC_CFG_REG, 0x0054
.equiv BUS_CLK_GATING_REG2, 0x0068
.equiv BUS_SOFT_RST_REG2, 0x02d0
.equiv PD, (0x24 * 3)
.equiv PORT_CFG0, 0x00
.equiv PORT_CFG1, 0x04
.equiv PORT_PUL0, 0x1c
.equiv TWI_ADDR, 0x00
.equiv TWI_XADDR, 0x04
.equiv TWI_DATA, 0x08
.equiv TWI_CNTR, 0x0c
.equiv TWI_STAT, 0x10
.equiv TWI_CCR, 0x14
.equiv TWI_SRST, 0x18
.equiv TWI_EFR, 0x1c
.equiv TWI_LCR, 0x20
.equiv SSD1306_ADDRESS, 0x78
.equiv SSD1306_LCDWIDTH, 128
.equiv SSD1306_LCDHEIGHT, 32
.equiv SSD1306_SETCONTRAST, 0x81
.equiv SSD1306_DISPLAYALLOW_RESUME, 0xa4
.equiv SSD1306_DISPLAYALLOW, 0xa5
.equiv SSD1306_NORMALDISPLAY, 0xa6
.equiv SSD1306_INVERTDISPLAY, 0xa7
.equiv SSD1306_DISPLAYOFF, 0xae
.equiv SSD1306_DISPLAYON, 0xaf
.equiv SSD1306_SETDISPLAYOFFSET, 0xd3
.equiv SSD1306_SETCOMPINS, 0xda
.equiv SSD1306_SETVCOMDETECT, 0xdb
.equiv SSD1306_SETDISPLAYCLOCKDIV, 0xd5
.equiv SSD1306_SETPRECHARGE, 0xd9
.equiv SSD1306_SETMULTIPLEX, 0xa8
.equiv SSD1306_SETLOWCOLUMN, 0x00
.equiv SSD1306_SETHIGHCOLUMN, 0x10
.equiv SSD1306_SETSTARTLINE, 0x40
.equiv SSD1306_MEMORYMODE, 0x20
.equiv SSD1306_COLUMNADDR, 0x21
.equiv SSD1306_PAGEADDR, 0x22
.equiv SSD1306_COMSCANINC, 0xc0
.equiv SSD1306_COMSCANDEC, 0xc8
.equiv SSD1306_SEGREMAP, 0xa0
.equiv SSD1306_CHARGEPUMP, 0x8d
.equiv SSD1306_EXTERNALVCC, 0x01
.equiv SSD1306_SWITCHCAPVCC, 0x02
.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 r1, =(1 << 20) | (1 << 16)
str r1, [r0, #BUS_CLK_GATING_REG2]
str r1, [r0, #BUS_SOFT_RST_REG2]
ldr r0, =GPIO_BASE
ldr r1, =0x3
str r1, [r0, #(PD + PORT_CFG0)]
ldr r1, =0x30000
str r1, [r0, #(PD + PORT_CFG1)]
ldr r0, =TWI0_BASE
ldr r1, =(2 << 3) | (3 << 0)
str r1, [r0, #TWI_CCR]
ldr r1, =1
str r1, [r0, #TWI_SRST]
0:
ldr r1, [r0, #TWI_SRST]
cmp r1, #0
bne 0b
ldr r1, =(1 << 6)
str r1, [r0, #TWI_CNTR]
ldr r0, =SSD1306_DISPLAYOFF
bl i2c_cmd
ldr r0, =SSD1306_SETDISPLAYCLOCKDIV
bl i2c_cmd
ldr r0, =0x80
bl i2c_cmd
ldr r0, =SSD1306_SETMULTIPLEX
bl i2c_cmd
ldr r0, =0x1F
bl i2c_cmd
ldr r0, =SSD1306_SETDISPLAYOFFSET
bl i2c_cmd
ldr r0, =0x00
bl i2c_cmd
ldr r0, =SSD1306_SETSTARTLINE
bl i2c_cmd
ldr r0, =SSD1306_CHARGEPUMP
bl i2c_cmd
ldr r0, =0x14
bl i2c_cmd
ldr r0, =SSD1306_MEMORYMODE
bl i2c_cmd
ldr r0, =0x00
bl i2c_cmd
ldr r0, =SSD1306_SEGREMAP | 0x01
bl i2c_cmd
ldr r0, =SSD1306_COMSCANDEC
bl i2c_cmd
ldr r0, =SSD1306_SETCOMPINS
bl i2c_cmd
ldr r0, =0x02
bl i2c_cmd
ldr r0, =SSD1306_SETCONTRAST
bl i2c_cmd
ldr r0, =0x8f
bl i2c_cmd
ldr r0, =SSD1306_SETPRECHARGE
bl i2c_cmd
ldr r0, =0xf1
bl i2c_cmd
ldr r0, =SSD1306_SETVCOMDETECT
bl i2c_cmd
ldr r0, =0x40
bl i2c_cmd
ldr r0, =SSD1306_DISPLAYALLOW_RESUME
bl i2c_cmd
ldr r0, =SSD1306_NORMALDISPLAY
bl i2c_cmd
ldr r0, =SSD1306_DISPLAYON
bl i2c_cmd
ldr r0, =SSD1306_COLUMNADDR
bl i2c_cmd
ldr r0, =0
bl i2c_cmd
ldr r0, =SSD1306_LCDWIDTH-1
bl i2c_cmd
ldr r0, =SSD1306_PAGEADDR
bl i2c_cmd
ldr r0, =0
bl i2c_cmd
ldr r0, =(SSD1306_LCDHEIGHT/8)-1
bl i2c_cmd
ldr r4, =512
0:
ldr r0, =0xff
bl i2c_dat
subs r4, #1
bne 0b
main:
b main
i2c_clr_intf:
push {r4, lr}
ldr r4, =TWI0_BASE
ldr r1, [r4, #TWI_CNTR]
bic r1, #0x08
str r1, [r4, #TWI_CNTR]
pop {r4, pc}
i2c_cmd:
push {r4, lr}
ldr r4, =TWI0_BASE
ldr r1, [r4, #TWI_CNTR]
orr r1, #(1 << 5)
str r1, [r4, #TWI_CNTR]
0:
ldr r1, [r4, #TWI_STAT]
cmp r1, #0x08
bne 0b
ldr r1, =SSD1306_ADDRESS
str r1, [r4, #TWI_DATA]
bl i2c_clr_intf
0:
ldr r1, [r4, #TWI_STAT]
cmp r1, #0x18
bne 0b
ldr r1, =0x00
str r1, [r4, #TWI_DATA]
bl i2c_clr_intf
0:
ldr r1, [r4, #TWI_STAT]
cmp r1, #0x28
bne 0b
str r0, [r4, #TWI_DATA]
bl i2c_clr_intf
0:
ldr r1, [r4, #TWI_STAT]
cmp r1, #0x28
bne 0b
ldr r1, [r4, #TWI_CNTR]
orr r1, #(1 << 4)
str r1, [r4, #TWI_CNTR]
bl i2c_clr_intf
0:
ldr r1, [r4, #TWI_STAT]
cmp r1, #0xf8
bne 0b
pop {r4, pc}
i2c_dat:
push {r4, lr}
ldr r4, =TWI0_BASE
ldr r1, [r4, #TWI_CNTR]
orr r1, #(1 << 5)
str r1, [r4, #TWI_CNTR]
0:
ldr r1, [r4, #TWI_STAT]
cmp r1, #0x08
bne 0b
ldr r1, =SSD1306_ADDRESS
str r1, [r4, #TWI_DATA]
bl i2c_clr_intf
0:
ldr r1, [r4, #TWI_STAT]
cmp r1, #0x18
bne 0b
ldr r1, =0x40
str r1, [r4, #TWI_DATA]
bl i2c_clr_intf
0:
ldr r1, [r4, #TWI_STAT]
cmp r1, #0x28
bne 0b
str r0, [r4, #TWI_DATA]
bl i2c_clr_intf
0:
ldr r1, [r4, #TWI_STAT]
cmp r1, #0x28
bne 0b
ldr r1, [r4, #TWI_CNTR]
orr r1, #(1 << 4)
str r1, [r4, #TWI_CNTR]
bl i2c_clr_intf
0:
ldr r1, [r4, #TWI_STAT]
cmp r1, #0xf8
bne 0b
pop {r4, pc}
.end
完成
