Question

我通过串口（UART）连接了笔记本电脑。我编写了函数ReadChar，它在UART的RXD端口上读取char作为输入，但它不起作用。运行时，即使我在控制台中写入内容，程序也会卡在ReadChar无限循环中等待某些数据。 WriteChar函数完全正常，所以我认为问题可能出在ReadChar函数或UART的初始化中。

谁可以帮我这个？

非常感谢。

主要功能：

main:
BL InitializeUART
BL ReadChar
BL WriteChar @ this function works properly</code>

ReadChar功能：

ReadChar:
LDR R0, =AUX_MU_LSR_REG
LDR R1, [R0]
TST R1, #1
BEQ ReadChar
LDR R0, =AUX_MU_IO_REG
LDR R1, [R0]        
MOV pc, lr

UART初始化

.equ AUX_ENABLES,   0x20215004
.equ AUX_MU_IER_REG,    0x20215044
.equ AUX_MU_CNTL_REG,   0x20215060
.equ AUX_MU_LCR_REG,    0x2021504C
.equ AUX_MU_MCR_REG,    0x20215050
.equ AUX_MU_IIR_REG,    0x20215048
.equ AUX_MU_BAUD_REG,   0x20215068
.equ GPPUD,    0x20200094
.equ GPPUDCLK0,    0x20200098
.equ GPCLR0,    0x20200028
.equ GPFSEL1,    0x20200004



InitializeUART:
PUSH {lr}
@ Enable UART
MOV R1, #1
LDR R0, =AUX_ENABLES
STR R1, [R0]
@ disable interrupts
MOV R1, #0
LDR R0, =AUX_MU_IER_REG
STR R1, [R0]
@ disable transmit/receive
MOV R1, #0
LDR R0, =AUX_MU_CNTL_REG
STR R1, [R0]
@ set 8 bits communication
MOV R1, #3
LDR R0, =AUX_MU_LCR_REG
STR R1, [R0]
@ set the RTS line high
MOV R1, #0
LDR R0, =AUX_MU_MCR_REG
STR R1, [R0]
@ leave disable interrupts
MOV R3, #0
LDR R0, =AUX_MU_IER_REG
STR R3, [R0]
@ clear the input and output buffers
MOV R1, #198
LDR R0, =AUX_MU_IIR_REG
STR R1, [R0]
@ set BAUD = 270
MOV R1, #200
ADD R1, R1, #70
LDR R0, =AUX_MU_BAUD_REG
STR R1, [R0]
@ Set GPIO line 14 for transmission (TXD)
LDR R0, =GPFSEL1
LDR R1, [R0]
BIC R3, R1, #28672
ORR R3, R3, #8192
STR R3, [R0]
@ Set GPIO line 15 for receiving (RXD)
LDR R1, [R0]
BIC R3, R1, #229376
ORR R3, R3, #65536
STR R3, [R0]
@ disable GPIO pull-up/down
MOV R1, #0
LDR R0, =GPPUD
STR R1, [R0]
@ wait for 150 cycles
MOV R1, #0
cycle1: ADD R1, R1, #1
BL Cycle
CMP R1, #150
BNE cycle1
@ Assert clock lines (14 & 15)
MOV R1, #16384  @ 1<<14
LDR R0, =GPPUDCLK0
STR R1, [R0]
MOV R1, #32768 @ 1<<15
STR R1, [R0]
@ wait for 150 cycles
MOV R1, #0
cycle2: ADD R1, R1, #1
BL Cycle
CMP R1, #150
BNE cycle2
@ clear clock lines
MOV R1, #0
LDR R0, =GPCLR0
STR R1, [R0]
@ enable bits 0 and 1 in CONTROL
MOV R1, #2
LDR R0, =AUX_MU_CNTL_REG
STR R1, [R0]
@ return
POP {pc}        

Cycle:      MOV pc, lr

Answer 1

我找到了解决方案。在初始化的最后一步中，仅启用发送器而不启用接收器。所以应该存储＃3（0b11）而不是＃2（0b10）。

@ enable bits 0 and 1 in CONTROL
MOV R1, #3
LDR R0, =AUX_MU_CNTL_REG
STR R1, [R0]

从装配中的Raspberry Pi的UART RxD读取

1 个答案: