Normally SPI's are good up to 100MHz, but this is seldom needed. I
normally set them up at 1MHz for initial debug (allows for cheaper
instruments) and then usually go to 10MHz which normally makes speed a
non-issue and allows for longer wires. 16MHz should be fine as well.
I2C's often run around 1MHz and are very dependent on length (i.e.
capacitance). One needs to keep I2Cs high when not used to minimize
power due to pull-ups. SPI's, once you get them going, are generally a
better choice.
On 2015-12-16 10:45 AM, William Hermans wrote:
Hmm according to that device tree source, max frequency is 16Mhz. I
thought the SPI was capable of 30Mhz or more. Maybe I'm remembering
wrongly.
On Wed, Dec 16, 2015 at 8:41 AM, Robert Nelson
<[email protected] <mailto:[email protected]>> wrote:
On Wed, Dec 16, 2015 at 9:31 AM, William Hermans
<[email protected] <mailto:[email protected]>> wrote:
/SPI works great on v4.1.x now, just pay attention this
this little/
/spi-dma-disable hack:/
//
/https://github.com/beagleboard/bb.org-overlays/blob/master/src/arm/BB-SPIDEV0-00A0.dts#L54/
//
/"ti,pio-mode;"/
//
/Otherwise, the spidev interface will lock up on the
160'th bit.../
//
/(3.8 never used dma on spi, so this isn't a regression in
speed..)/
Is it possible to control the SPI hardware through the PRU,
and if so, would that hack still matter Robert ? No idea if
spidev is used in such a case or not . . .
I didn't investage that side.. It's just when used as an overlay,
that's needed..
If you setup a *.dtb with spi enabled in the dtb-rebuilder you
don't need that workaround..
https://github.com/RobertCNelson/dtb-rebuilder/blob/4.1-ti/src/arm/am335x-boneblack-spi0.dts#L140
Regards,
--
Robert Nelson
https://rcn-ee.com/
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