STM32F4串口在8倍过采样和16倍过采样下，各种常用波特率误差和实际速度
串口外设主频配置为84MHz。LUA代码：
BspArray =
{
110,
300,
600,
1200,
2400,
4800,
9600,
19200,
38400,
57600,
115200,
128000,
230400,
256000,
460800,
500000,
512000,
600000,
750000,
921600,
1000000,
1152000,
1500000,
2000000,
2500000,
3000000
}
Fclk = 84000000-- 用户设置串口外设主频
OVER8 = 0 -- 0表示16过采样，1表示8倍过采样
print("所需波特率 实际值波特率 误差 BRR寄存器数值")
for i=1, #BspArray, 1 do
Bsp = BspArray
UARRTDIV = Fclk/(8*(2-OVER8))/Bsp
mantissa = UARRTDIV//1
fraction = UARRTDIV - mantissa
if(OVER8 == 0) then
fraction_adj = (fraction*16 + 0.5)//1
if(fraction_adj > 16) then
fraction_adj = 0
mantissa = mantissa + 1
end
Bsp1 = Fclk/(8*(2-OVER8))/(mantissa+ fraction_adj/16)
str = string.format("%-13d %-13.4f %7.4f%% %-.4f = 0x%08x",
Bsp, Bsp1, (Bsp1-Bsp)/Bsp*100, mantissa+fraction_adj/16, mantissa*16+fraction_adj)
print(str)
else
fraction_adj = (fraction*8 + 0.5)//1
if(fraction_adj > 8) then
fraction_adj = 0
mantissa = mantissa + 1
end
Bsp1 = Fclk/(8*(2-OVER8))/(mantissa+ fraction_adj/8)
str = string.format("%-13d %-13.4f %7.4f%% %-.4f=0x%08x",
Bsp, Bsp1, (Bsp1-Bsp)/Bsp*100, mantissa+fraction_adj/8, mantissa*16+fraction_adj)
print(str)
end
end
16过采样的误差率和实际速度如下 :
所需波特率 实际值波特率 误差 BRR寄存器数值
110 110.0001 0.0000% 47727.2500 = 0x000ba6f4
300 300.0000 0.0000% 17500.0000 = 0x000445c0
600 600.0000 0.0000% 8750.0000 = 0x000222e0
1200 1200.0000 0.0000% 4375.0000 = 0x00011170
2400 2400.0000 0.0000% 2187.5000 = 0x000088b8
4800 4800.0000 0.0000% 1093.7500 = 0x0000445c
9600 9600.0000 0.0000% 546.8750 = 0x0000222e
19200 19200.0000 0.0000% 273.4375 = 0x00001117
38400 38391.2249 -0.0229% 136.7500 = 0x0000088c
57600 57613.1687 0.0229% 91.1250 = 0x000005b2
115200 115226.3374 0.0229% 45.5625 = 0x000002d9
128000 128048.7805 0.0381% 41.0000 = 0x00000290
230400 230136.9863 -0.1142% 22.8125 = 0x0000016d
256000 256097.5610 0.0381% 20.5000 = 0x00000148
460800 461538.4615 0.1603% 11.3750 = 0x000000b6
500000 500000.0000 0.0000% 10.5000 = 0x000000a8
512000 512195.1220 0.0381% 10.2500 = 0x000000a4
600000 600000.0000 0.0000% 8.7500 = 0x0000008c
750000 750000.0000 0.0000% 7.0000 = 0x00000070
921600 923076.9231 0.1603% 5.6875 = 0x0000005b
1000000 1000000.0000 0.0000% 5.2500 = 0x00000054
1152000 1150684.9315-0.1142% 4.5625 = 0x00000049
1500000 1500000.0000 0.0000% 3.5000 = 0x00000038
2000000 2000000.0000 0.0000% 2.6250 = 0x0000002a
2500000 2470588.2353-1.1765% 2.1250 = 0x00000022
3000000 3000000.0000 0.0000% 1.7500 = 0x0000001c
8过采样的误差率和实际速度如下 :
所需波特率 实际值波特率 误差 BRR寄存器数值
110 110.0001 0.0000% 95454.5000=0x00174de4
300 300.0000 0.0000% 35000.0000=0x00088b80
600 600.0000 0.0000% 17500.0000=0x000445c0
1200 1200.0000 0.0000% 8750.0000=0x000222e0
2400 2400.0000 0.0000% 4375.0000=0x00011170
4800 4800.0000 0.0000% 2187.5000=0x000088b4
9600 9600.0000 0.0000% 1093.7500=0x00004456
19200 19200.0000 0.0000% 546.8750=0x00002227
38400 38391.2249 -0.0229% 273.5000=0x00001114
57600 57613.1687 0.0229% 182.2500=0x00000b62
115200 115226.3374 0.0229% 91.1250=0x000005b1
128000 128048.7805 0.0381% 82.0000=0x00000520
230400 230136.9863 -0.1142% 45.6250=0x000002d5
256000 256097.5610 0.0381% 41.0000=0x00000290
460800 461538.4615 0.1603% 22.7500=0x00000166
500000 500000.0000 0.0000% 21.0000=0x00000150
512000 512195.1220 0.0381% 20.5000=0x00000144
600000 600000.0000 0.0000% 17.5000=0x00000114
750000 750000.0000 0.0000% 14.0000=0x000000e0
921600 923076.9231 0.1603% 11.3750=0x000000b3
1000000 1000000.0000 0.0000% 10.5000=0x000000a4
1152000 1150684.9315-0.1142% 9.1250=0x00000091
1500000 1500000.0000 0.0000% 7.0000=0x00000070
2000000 2000000.0000 0.0000% 5.2500=0x00000052
2500000 2470588.2353-1.1765% 4.2500=0x00000042
3000000 3000000.0000 0.0000% 3.5000=0x00000034
页:
[1]