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by Genwolf
Thu Jan 16, 2020 7:04 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Maximum GPIO frequency from kernel space
Replies: 7
Views: 403

Re: Maximum GPIO frequency from kernel space

joan wrote:
Thu Jan 16, 2020 8:35 am
You need hardware support as software based reads will be subject to Linux jitter.
What do you mean by hardware support ? Will there still be considerable jitter if i read the gpios from kernel (using DMA perhaps)?
by Genwolf
Thu Jan 16, 2020 8:10 am
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Maximum GPIO frequency from kernel space
Replies: 7
Views: 403

Re: Maximum GPIO frequency from kernel space

I know that frequencies higher than 20MHz are imposible on the gpios from user space. Not true, 50MHz PWM even on Pi Zero is clean, verified with 400Msps logic analyzer: https://www.raspberrypi.org/forums/viewtopic.php?p=1087893#p1087893 https://pbs.twimg.com/media/C0or7cXWIAAChr-.jpg It was my fir...
by Genwolf
Thu Jan 16, 2020 8:06 am
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Maximum GPIO frequency from kernel space
Replies: 7
Views: 403

Re: Maximum GPIO frequency from kernel space

joan wrote:
Wed Jan 15, 2020 8:51 pm
I've seen people claim more than 20 MHz from user land.

Define stable frequency.
The frequency at which i can read the actual states of the gpios without any interuptions for relatively long time (let's say 5 minutes).
by Genwolf
Wed Jan 15, 2020 7:15 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Maximum GPIO frequency from kernel space
Replies: 7
Views: 403

Maximum GPIO frequency from kernel space

Hello,
I know that frequencies higher than 20MHz are imposible on the gpios from user space. Is that different when using the gpios from kernel space? Could I achieve higher stable frequencies for interfacing with a ADC for example?

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