Do I need to use HSE when enabling DSIHOST?

[DMårt]

I have CubeMX 2.0.0 and I notice that if I want to enable DSIHOST, I need to first enable HSE.

But the clock configuration of the DSI does not require HSE. It seems that the clock configuration of DSI seems to work with HSI in CubeMX 2.0.0.

So, the question is: I need to enable HSE, but do I need to clock configure it for DSI as well? Or could I use HSI in the clock configuration, even if HSE is enabled?

Processor: STM32MP257FAK3

[Olivier GALLIEN]

Hi @DMårt , 

CubeMX 2.0.0 does not exist.

Do you mean CuIDE 2.0 / or CubeMX 6.16  ? 

Olivier 

[DMårt]

@Olivier GALLIEN 

I mean the latest CubeMX that I have recently downloaded for 2 days ago.

I found out that I need to use HSE, but it still a "hack" that you can still use HSI, even if HSE is activated inside RCC.

[AScha.3 · Accepted solution]

The basic problem is the precision of the clock , frequency and jitter.

So for hi speed connections usually you should choose the best you can get,

and this is a low jitter crystal source for the PLLs , not a RC or gate delay based clock.

But if you prefer to try out, what might go wrong with more jitter, just try it.

So the "need to use HSE" is just a indicator to go the reliable way , using a low jitter master clock.

I would never have the idea to drive a high speed complex SOC with a clock, that saves about 80 ct , but at the risk many things break connection , when temperature changes or it ages just some weeks.

I always choose a crystal or mems oscillator , not even a simple crystal, and RC is absolute no go.

ymmv.

[DMårt]

@AScha.3 @Olivier GALLIEN 

Thanks!

I have selected a footprint for mounting a SMD2016-P4 to SMD2520-P4 oscillator. 

In this case it's going to be 24MHz, due to save cost. The HDMI and USB also have the same MHz of ocillator. 

I don't know if they could share the same oscillator. Perhaps not...