CAN采样点设置为多少合适？设置不对会咋样？

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网上有人说道：

（1）一般配置在75-80%的位置

（2）选择采样点位置在85%左右为佳

（3）

75%     when 波特率 > 800K
80%     when 波特率 > 500K
87.5%   when 波特率 <= 500K

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那么到底是多少呢？

本博主在ISO11898-1没有找到确切的值。但是cia官网找到了（http://www.can-cia.org/index.php?id=systemdesign-can-physicallayer&L=1&amp%3BL=3）：

The CAN bit comprises – depending on the configured “atomic” time unit called time quantum (tq) – multiple of these time quanta. The time quanta length derives from the bit-rate prescaler and the used oscillator frequency.

The CAN bit is logically divided into four segments. The synchronization segment has always a length of 1 tq. The following propagation segment and phase-segment 1 are not distinguishable for the user. It is configured as one value. The forth part is the phase-segment 2. Between the two phase-segments, the sample-point is located. If the bit-timing settings move the sample-point to the end of the bit, the propagation segment is enlarged, so that you can realize longer networks. If the sample-point is configured in the other direction, the re-synchronization capability is increased.

The sample point should be the same in all connected CAN nodes. However, in practice it is sufficient if the sample points don't vary too much. The automotive industry has specified some recommendations for the bit timing settings in the SAE J2284 series. For CANopen networks, the recommendations given in CiA 301 should be used. The sample points should be at 87,5 percent of the bit time. For most of the specified bit-rates a range of 85 percent to 90 percent is allowed. Of course, the larger the tolerance range, the shorter the maximum possible length of the network。

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本博主由于工作的关系，得以接触到各种厂商的can设备，测试都是在80%以上，如81.25之类的。另外，老外的can分析仪都是80%以上。

看了上面的英文就弄懂了采样点的作用了。是关于重同步的。如果can采样点选取合适，can总线就能容纳更多的can节点。因此极其重要。

至于我的STM32设置成多少，明天再议，肯定是80%-87.5之间了。

75%

when

波特率

> 800K

80%

when

波特率

> 500K

87.5%

when

波特率

<= 500K

75%

when

波特率

> 800K

80%

when

波特率

> 500K

87.5%

when

波特率

<= 500K

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