这一点很重要，因为使用 1 倍探头会大幅降低带宽。

你的 SPI 时钟频率设置为 100MHz，需要一台性能良好的示波器才能正确显示信号。构成方波的谐波是奇次谐波，因此示波器的带宽需要远大于 100MHz，并且采样率也要与之匹配。

所以在我看来，你示波器上的波形看起来并不算异常，尤其考虑到 3.3V 的信号经过截止频率约为 6MHz 的一阶探头滤波器衰减后，其幅度会远小于 3.3V 的输出电压。

Translated from English:
I'm not familiar with keysight scopes, but am I right when saying that the signal is probed with a 1x probe instead of 10x.
Why this is important, is that with a 1x probe the bandwidth is reduced quite a bit.
With your SPI clock set to 100MHz one needs a good scope to see a proper representation of the signal. The harmonics that make up the square wave are the odd ones, so the scope needs to have a bandwidth of way more than 100MHz and a sampling rate to go with it.
So to me the trace on your scope does not look that abnormal, also considering that a 3.3V signal reduced by a first order probe filter with a cutoff point around 6MHz will be far less than the 3.3V output.