Is there any restricts on SPI feature on Necleo L053R8?

[SLiu.10]

I set the SPI on L053R8 works in slave mode. When the master's clock less than 800KHz, slaver can read/write data success. But when I change the master's clock to 1.6MHz, the L053R8 cannot read one byte any more which is correct, each byte is '0xFF'. I have tried to increase the sysclock of L053R8, but nothing changes.

[Uwe Bonnes]

I suspect some problem with your GPIO settings or the wiring. Perhaps ground is missing or the GPIO is set as Open Drain. If the connection is of board, wire length will also have an influence.

[SLiu.10]

Thanks for your reply.

First, ground is always connected, or it wouldn't work when clock is 800KHz.

Second, the source code is intact sample code downloaded form st.com, so I don't think there is any mistake on GPIO configuration.

For the wire length, I am using the Dupont Line about 15cm, and it works well on other SPI devices with high frequency clock. So I‘m very puzzled on it:\ .