Author Topic: De-rating of SPI master clock frequency  (Read 263 times)

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Offline Wilson__Topic starter

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De-rating of SPI master clock frequency
« on: June 08, 2024, 05:12:50 pm »
What is your 'de-rating' (setting 'safer' than data sheet) experience in setting 4-wires SPI master clock frequency?   

The sensor data sheet says 17MHz.  Factory support person says 2 to 10MHz.  The demo board (which we do not have) is 7_5MHz in driver software (presume 7.5MHz).

MCU and sensor within 1.5 inches (50mm).  Only MCU and one sensor, 3 volts push-pull I/O.   No long wiring to multiple sensors.  Cell life limited.  We like transfer as fast as safely possible so devices can sleep soonest.

Many thanks
 

Offline globoy

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Re: De-rating of SPI master clock frequency
« Reply #1 on: June 08, 2024, 05:30:31 pm »
Certainly 50mm is not too long for a SPI bus even at 17 MHz.

Perhaps the sensor has some tight SPI timing that leads the support person to suggest a maximum of 10 MHz.  I'd look at the SPI section of the spec sheets for both the sensor and the micro-controller.  Things you want to look at include any clock duty cycle requirements on the sensor and capabilities of the MCU; setup and hold times for both MISO and MOSI both being sourced and received.  Perhaps this will explain why the support person said 10 MHz max.

But maybe the micro running at something like 16 MHz would work fine with the sensor.  If the spec timings lined up, I'd have no worries about running - or at least trying - that rate given a 17 MHz spec'd max.
 
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