Can not set L6470 register

[Jhan.1]

Hello, I am trying to use L6470 for stepper motor control.

I tried to change L6470's step mode register from 0x07(reset value) to 0x05.

But when I read it back after I sent a command, its value was the same.

I use 6 L6470 chips but this problem happened to only 2 chips.

This means the firmware was correct but there are some problems with my PCB board.

Thus, Here I have a question about the register setting.

Which situation cause this problem?! is there anybody who knows about this?

[Cristiana SCARAMEL]

Hi @Jhan.1​ and welcome to the ST Community.

Could you share more details on your application?

Are you using a custom board and/or custom firmware?

For now I can suggest to refer to the application notes AN4290.

In the paragraph 2 you can find more details on the daisy chain connection and configuration to drive multiple devices with a single SPI interface.

EDIT: please not that the STEP_MODE register is writable only when outputs are in high impedance.

Let me know if these info are useful to you.

[Jhan.1]

Thank you Cristiana, your answer really helped me!!

As you suggested, when I let L6470 be Hi-Z state, I can write registers.

Maybe there were some problems when it turned on.