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by livius147
Fri Nov 09, 2018 1:08 pm
Forum: Advanced users
Topic: spidev implementation
Replies: 5
Views: 419

Re: spidev implementation

Hi! I have already properly set the spidev device with a similar code (by setting the max frequency, bits per word, the clock edge mode and so on). The behavior I have described follow those initialization procedures. The problems are present when the ioctl, to transfer data, is called. Regards. Liv...
by livius147
Fri Nov 09, 2018 9:52 am
Forum: Advanced users
Topic: spidev implementation
Replies: 5
Views: 419

Re: spidev implementation

I analyzed the clock and the SPI signals. Another strange behavior: Up to 78 ms the SCLK signal is completely unrealiable: https://www.raspberrypi.org/forums/download/file.php?mode=view&id=26072 Then the SCLK becomes stable: https://www.raspberrypi.org/forums/download/file.php?mode=view&id=26071 Did...
by livius147
Fri Nov 09, 2018 9:29 am
Forum: Advanced users
Topic: spidev implementation
Replies: 5
Views: 419

spidev implementation

Hi all, I am trying to use the spidev device (via the kernel interface linux/spi/spidev.h). This interface produces strange behaviors: 1) when I send a single byte, or a couple of bytes, the SCLK does not comply with my specifications. I set 8MHz SCLK and the generated clock is 4-5MHz. 2) when I sen...
by livius147
Thu Oct 25, 2018 8:55 pm
Forum: Advanced users
Topic: SPI clock unreliable over 8MHz
Replies: 3
Views: 1526

Re: SPI clock unreliable over 8MHz

Thanks for your reply!

Are you recording the GPIO11 (the SCLK of the firt SPI unit), pin 23 of raspberry 3? Which code did you use to generate that waveform?
Which version of linux are you using? Raspbian with the latest kernel?
I tested spidev and bcm2845 without getting good results.

Regards.
by livius147
Thu Oct 25, 2018 7:07 am
Forum: Advanced users
Topic: SPI clock unreliable over 8MHz
Replies: 3
Views: 1526

SPI clock unreliable over 8MHz

Dear all, I am currently using RPI3b and RPI3b+. I am trying to drive an external acquisition IC (ads1299) which is connected to the RPI boarda via SPI. I tried to use the SPI @4 MHz @8 MHz and @16MHz: the system seems to be unreliable when the SCLK frequency is greater than 8 MHz. The datasheet sho...

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