Max SPI clock rate on T4.1

strud

Well-known member
Hi All,

I'm trying to find the highest clock freq I can run on the T4.1. Is this determined by the hardware or limitations in the SPI library?

I'm a bit bamboozled as to where I should be looking.

Thanks

Craig
 
There have been some anecdotal notes in prior threads - seems it is near 60 MHz - it can clock a bit higher but seems the returns were diminishing or limited.

Can't say if it was the device at hand or the processor that was maxed out.
 
The datasheet says on page 67 "maximum frequency of operation (fop) is 30 MHz" (footnote 1).

Higher speeds often work in practice, but as far as official specs go, any LPSPI clock over 30 MHz would technically be considered overclocking.

FlexSPI can go much higher. Several different maximum speeds are given on page 47-49, depending on settings.
 
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I agree with defragster at maybe 60. But a lot depends on on how short the io needs to transfer…

Maybe you remember the device at hand? A display or Camera and if T_4.x or T_MM? Seems it got pushed to 72 or 84 and seemed to be functionaing - but no faster than at the ~60 number.

Was going to mention @tonton81's SPI_MSTransfer code that lets Teensy talk to a Teensy - not sure how fast that can go { github.com/tonton81/SPI_MSTransfer shows tested 4-40 MHz - but ReadMe suggest it is only on T_3.x's - but it seems the Slave side involved some overhead that might be a limiting factor.
 
Thanks all, very useful input.

I'm currently running a 4ch 24bit ADC from TI with a sample rate of 32KHz and I'm using an SPI clock of 16MHz and this is quite adequate. I plan to run a similar design with a similar ADC that supports 128kHz sample rate so wanted to wind up the SPI clock a little to ensure it isn't 'running all the time'.
 
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