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reini87_coffee2code
reini87_coffee2code
Associate
August 16, 2019
Question

Is ther a possibility to search for MCU's by peripheral (SPI) speed?

  • August 16, 2019
  • 4 replies
  • 1393 views

Hello everybody!

This is my first post. I hope that i am on the right corner of this Q&A section.

For an application i need a MCU that is capable to run the SPI with a clock-frequency of at least 80MHz (Master transmit) and at least 50MHz (Master receive).

Now my problem is that all microcontroller i've used are limited in SPI-Speed (Master/Slave) far below this frequency.

Right now i've only found MCU's of the H7-series (randomly searched) that would achieve that SPI frequencies. But i think that the H7-series is mutch to powerful for my needings in all other aspects. I just need to write a few register via SPI with that high speed. Nothing more. well, and some timing for the register writing...not that effort.

Now my question is, if there is a way (on the homepage) to select MCU's via their peripheral speed/frequency (SPI in my case) so that i can pick a lower powered MCU that will also achieve this SPI frequency (like H7-series).

Or maybe some of you have already faced the same problem and could give me a tip where to search.

Thanky in advance

This topic has been closed for replies.

4 replies

waclawek.jan
waclawek.jan
Super User
August 16, 2019

In the vast majority of STM32 the SPI SCK clock is derived from the respective APB clock, which is usually constrained to around 100MHz; i.e. no 80MHz SCK available.

The 'H7 is AFAIK unique amongst STM32s in that there's an independent SPI "kernel clock" from which the SPI SCK is derived, that's why it can go higher in frequency.

JW

Jack Peacock_2
Jack Peacock_2
Associate II
August 16, 2019

What SPI peripheral needs speeds that high on an M class controller? If it's a sensor or FPGA, where is the data coming from on the MCU side that will keep up with something that fast? That's >12MB/sec transmit and >6MB/sec receive. DMA can handle rates like that but there's no time left over to process it unless you have a fast MCU to start...like an H7.

If the target is a serial NOR there are better ways to achieve the same transfer rate. Either a QSPI, interleaved QSPI or octo-SPI to widen the bus, and double data rate to transfer on both clock edges. A QSPI DDR can support 12.5MB/sec at a clock speed of 25MHz with an SPI /2 prescaler, well within STM32 specs without going to the H7.

Jack Peacock

S.Ma
S.Ma
Principal
August 17, 2019

If SPI 80MHz is what you need and no other MCU peripheral is better suited to the task, you shall look for STM32 with double core frequency (160MHz), and then check the GPIO speed as 80 MHz is quite within the signal integrity and power bounce territory. Keep ground loops areas as small as possible.

reini87_coffee2code
reini87_coffee2codeAuthor
Associate
August 29, 2019

Hello,

sorry for my late response. I have been in holiday until now.

Thank you for your answers.

I want to make sure that i will meet the highest possible communication speed with the connected device.

It might not be necessary in the future to meet this high communication speed but for now my approach is to

get it all and reduce power later if possible.

I have orderd a board with a H7 MCU on it. Lets see how it works.

This community is great.

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