STM32H7串口的BRR波特率寄存器是16bit，有最小波特率支持限制

eric2013

1、比如串口外设配置主频是100M，16bit过采样，那么最小波特率就在1200bps和2400之间，BRR最大值65535

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所需波特率    实际值波特率    误差     BRR寄存器数值
110           110.0000      -0.0000%   909091.0000 = 0x000ddf23
300           300.0003       0.0001%   333333.0000 = 0x00051615
600           599.9988      -0.0002%   166667.0000 = 0x00028b0b
1200          1200.0048      0.0004%   83333.0000 = 0x00014585
2400          2399.9808     -0.0008%   41667.0000 = 0x0000a2c3
4800          4800.0768      0.0016%   20833.0000 = 0x00005161
9600          9599.6928     -0.0032%   10417.0000 = 0x000028b1
19200         19201.2289     0.0064%   5208.0000 = 0x00001458
38400         38402.4578     0.0064%   2604.0000 = 0x00000a2c
57600         57603.6866     0.0064%   1736.0000 = 0x000006c8
115200        115207.3733    0.0064%   868.0000 = 0x00000364
128000        128040.9731    0.0320%   781.0000 = 0x0000030d
230400        230414.7465    0.0064%   434.0000 = 0x000001b2
256000        255754.4757   -0.0959%   391.0000 = 0x00000187
460800        460829.4931    0.0064%   217.0000 = 0x000000d9
500000        500000.0000    0.0000%   200.0000 = 0x000000c8
512000        512820.5128    0.1603%   195.0000 = 0x000000c3
600000        598802.3952   -0.1996%   167.0000 = 0x000000a7
750000        751879.6992    0.2506%   133.0000 = 0x00000085
921600        917431.1927   -0.4523%   109.0000 = 0x0000006d
1000000       1000000.0000   0.0000%   100.0000 = 0x00000064
1152000       1149425.2874  -0.2235%   87.0000 = 0x00000057
1500000       1492537.3134  -0.4975%   67.0000 = 0x00000043
2000000       2000000.0000   0.0000%   50.0000 = 0x00000032
2500000       2500000.0000   0.0000%   40.0000 = 0x00000028
3000000       3030303.0303   1.0101%   33.0000 = 0x00000021

2、串口外设配置主频是10M，16bit过采样，那么最小波特率就在300bps和600之间，BRR最大值65535

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所需波特率    实际值波特率    误差     BRR寄存器数值
110           110.0001       0.0001%   181818.0000 = 0x0002c63a
300           299.9985      -0.0005%   66667.0000 = 0x0001046b
600           600.0060       0.0010%   33333.0000 = 0x00008235
1200          1199.9760     -0.0020%   16667.0000 = 0x0000411b
2400          2400.0960      0.0040%   8333.0000 = 0x0000208d
4800          4799.6160     -0.0080%   4167.0000 = 0x00001047
9600          9601.5362      0.0160%   2083.0000 = 0x00000823
19200         19193.8580    -0.0320%   1042.0000 = 0x00000412
38400         38387.7159    -0.0320%   521.0000 = 0x00000209
57600         57636.8876     0.0640%   347.0000 = 0x0000015b
115200        114942.5287   -0.2235%   174.0000 = 0x000000ae
128000        128205.1282    0.1603%   156.0000 = 0x0000009c
230400        229885.0575   -0.2235%   87.0000 = 0x00000057
256000        256410.2564    0.1603%   78.0000 = 0x0000004e
460800        465116.2791    0.9367%   43.0000 = 0x0000002b
500000        500000.0000    0.0000%   40.0000 = 0x00000028
512000        512820.5128    0.1603%   39.0000 = 0x00000027
600000        606060.6061    1.0101%   33.0000 = 0x00000021
750000        740740.7407   -1.2346%   27.0000 = 0x0000001b
921600        909090.9091   -1.3573%   22.0000 = 0x00000016
1000000       1000000.0000   0.0000%   20.0000 = 0x00000014
1152000       1176470.5882   2.1242%   17.0000 = 0x00000011
1500000       1538461.5385   2.5641%   13.0000 = 0x0000000d
2000000       2000000.0000   0.0000%   10.0000 = 0x0000000a
2500000       2500000.0000   0.0000%   8.0000 = 0x00000008
3000000       2857142.8571  -4.7619%   7.0000 = 0x00000007

supertankhzt

正常不会用到这么慢的波特率吧？

eric2013

supertankhzt 发表于 2025-9-25 13:54
正常不会用到这么慢的波特率吧？

对，一般用不到，今天遇到了这么一个问题，分享下。

SuGuolin

supertankhzt 发表于 2025-9-25 13:54
正常不会用到这么慢的波特率吧？

2400在水电表类很常见，1200也有

eric2013

SuGuolin 发表于 2025-9-26 09:02
2400在水电表类很常见，1200也有

网友抓包了一个连续波形输出，只有100-300Hz，感觉应该不是串口，很少用这么低的串口波特率