232 lines
5.7 KiB
Markdown
232 lines
5.7 KiB
Markdown
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### <mark>注意</mark>：
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* 在使用串口发送指令时，底层超过 **1s** 没有接收到上位机的指令，会向上位机返回错误状态码FF (error状态:连接超时），此时用户如果想要重新控制车辆，需要发送Reset命令
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* 在调试发送指令时，先发一条Reset命令，然后接着发指令，如:
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0x 55 AA 02 02 05 00 FA
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0x 55 AA 09 00 01 00 04 00 00 00 00 00 00 F3
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0x 55 AA 02 02 05 00 FA
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0x 55 AA 09 00 01 00 04 00 00 00 00 00 00 F3
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...
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#### 串口测试速度指令样例
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##### 左转
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55 AA 02 02 05 00 FA 55 AA 09 00 01 00 00 00 04 00 00 00 00 F3
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##### 右转
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55 AA 02 02 05 00 FA 55 AA 09 00 01 00 04 00 00 00 00 00 00 F3
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##### 前进
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55 AA 02 02 05 00 FA 55 AA 09 00 01 00 04 00 04 00 00 00 00 F7
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##### 后退
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55 AA 02 02 05 00 FA 55 AA 09 00 01 FF FA FF FA 00 00 00 00 F7
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下面列出几个常用的控制指令示例：
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# 控制车轮速度指令
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假设请求左车轮速度为0.1m/s，传输数据帧内容为：
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0x 55 AA 09 00 01 00 04 00 00 00 00 00 00 F3
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<table>
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<tbody>
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<tr align="center">
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<td rowspan="2">Header</td>
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<td rowspan="2">Length</td>
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<td rowspan="2">Sequence</td>
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<td colspan="5">Payload</td>
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<td rowspan="2">Checksum </td>
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</tr>
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<tr align="center">
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<td width="10%">MsgID</td>
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<td colspan="4">PARAM</td>
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</tr>
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<tr align="center">
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<td>55 AA</td>
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<td>09</td>
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<td>00</td>
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<td>01</td>
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<td>00 04</td>
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<td>00 00</td>
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<td>00 00</td>
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<td>00 00</td>
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<td>F3</td>
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</tr>
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<tr align="center">
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<td>起始标志位</td>
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<td>有效数据的长度为9个字节</td>
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<td>第一个指令</td>
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<td>控制车轮速度指令</td>
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<td>左车轮</td>
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<td>右车轮</td>
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<td colspan="2">固定不变为0</td>
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<td>异或校验码</td>
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</tr>
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</tbody>
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</table>
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如上文所说，通常我们所说的速度是以m/s为单位的速度，而指令中车轮速度的参数实际上是单位时间内期望编码器的计数，在此需要将指令的速度V（m/s）结合AP1下位机的物理参数进行计算，下面是车轮速度换算方法。
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M1下位机物理参数如下表：
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名称 | 参数 | 说明
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:-------------: | :-------------: | :-------------
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wheel_diameter | 0.25 | 车轮直径，单位：米
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encoder_resolution | 1600 | 编码器转一圈产生的脉冲数
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PID_RATE | 50 | PID调节PWM值的频率
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假设我们给M1左轮V=0.1m/s的速度（右轮速度的计算指令与此相同），<a name="caculate-method">计算方法</a>如下：
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车轮转动一圈，移动的距离为轮子的周长：
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distance_one_round
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=wheel_diameter*π
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=wheel_diameter*3.1415926
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=0.25*3.1415926
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车轮转动一圈，编码器产生的脉冲数为：
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wheel_encoder_resolution
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=1*encoder_resolution
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=1*1600
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=1600
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注：编码器与车轮连接在一起，车轮转1圈，编码器转1圈；编码器的脉冲数可以理解为编码器计数，编码器自转一圈计数1600，则车轮转一圈编码器计数为1600。
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所以AP1每移动1米产生脉冲数（编码器的计数）为:
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ticks_per_meter
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=(1/distance_one_round)*wheel_encoder_resolution
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=1/(0.25*3.1415926)*1600
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=2037.18
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又因为PID的频率是1秒钟50次，所以指令的参数计算方法为:
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int(V*ticks_per_meter/PID_RATE)
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=int(0.1*2037.18/50)
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=4
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用户可直接使用0.1m/s速度的计算结果来对应自己期望的速度换算成相应的数值，如0.2m/s为8，1m/s为40等。
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接着将计算出来的4换算为16进制为：
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00 04
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则速度指令的PARAM为
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00 04 00 00 00 00 00 00
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注：如果用户发送的速度超过了最大速度，则会按最大速度行进。
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# 获取电池电量指令
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0x 55 AA 02 01 02 00 FE
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<table>
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<tbody>
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<tr align="center">
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<td rowspan="2">Header</td>
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<td rowspan="2">Length</td>
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<td rowspan="2">Sequence</td>
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<td colspan="2">Payload</td>
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<td rowspan="2">Checksum </td>
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</tr>
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<tr align="center">
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<td>MsgID</td>
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<td>PARAM</td>
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</tr>
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<tr align="center">
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<td>55 AA</td>
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<td>02</td>
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<td>01</td>
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<td>02</td>
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<td>00</td>
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<td>FE</td>
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</tr>
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<tr align="center">
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<td>起始标志位</td>
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<td>有效数据的长度为2个字节</td>
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<td>第二个指令</td>
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<td>小车的电量请求</td>
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<td>参数为00</td>
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<td>异或校验码</td>
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</tr>
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</tbody>
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</table>
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# 重置状态指令
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当接收到下位机发送的错误状态码FF时，需要将AP1状态重置（Reset)，才能重新恢复控制，指令如下：
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0x 55 AA 02 02 05 00 FA
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<table>
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<tbody>
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<tr align="center">
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<td rowspan="2">Header</td>
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<td rowspan="2">Length</td>
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<td rowspan="2">Sequence</td>
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<td colspan="2">Payload</td>
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<td rowspan="2">Checksum </td>
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</tr>
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<tr align="center">
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<td>MsgID</td>
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<td>PARAM</td>
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</tr>
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<tr align="center">
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<td>55 AA</td>
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<td>02</td>
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<td>02</td>
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<td>05</td>
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<td>00</td>
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<td>FA</td>
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</tr>
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<tr align="center">
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<td>起始标志位</td>
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<td>有效数据的长度为2个字节</td>
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<td>第三个指令</td>
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<td>重置状态指令</td>
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<td>参数为00</td>
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<td>异或校验码</td>
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</tr>
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</tbody>
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</table>
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# 清除编码器计数指令
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0x 55 AA 02 03 06 00 F8
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<table>
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<tbody>
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<tr align="center">
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<td rowspan="2">Header</td>
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<td rowspan="2">Length</td>
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<td rowspan="2">Sequence</td>
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<td colspan="2">Payload</td>
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<td rowspan="2">Checksum </td>
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</tr>
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<tr align="center">
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<td>MsgID</td>
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<td>PARAM</td>
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</tr>
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<tr align="center">
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<td>55 AA</td>
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<td>02</td>
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<td>03</td>
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<td>06</td>
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<td>00</td>
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<td>F8</td>
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</tr>
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<tr align="center">
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<td>起始标志位</td>
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<td>有效数据的长度为2个字节</td>
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<td>第四个指令</td>
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<td>请求清除编码器计数</td>
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<td>参数为00</td>
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<td>异或校验码</td>
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</tr>
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</tbody>
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</table>
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