From the (not so clear) device tree binding docs. The ehrpwm docs say the last
number is flags and only PWM_POLARITY_INVERTED is supported. The generic PWM
bindings doc says "pwm-specifier typically encodes the chip-relative PWM number
and the PWM
period in nanoseconds." So since the EHRPWMs have an A and B channel, the first
number can be 0 or 1. The second number is the default period for the PWM.
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/devicetree/bindings/pwm/pwm-tiehrpwm.txt
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/devicetree/bindings/pwm/pwm.txt
On 10/3/19 1:59 PM, Mark A. Yoder wrote:
David:
Thanks. I did not. How do I discover what those values ( 1 500000 0) are?
--Mark
On Thursday, October 3, 2019 at 2:57:38 PM UTC-4, David Lechner wrote:
Did you also change pwms = <&ehrpwm1 *0* 500000 0>; to pwms = <&ehrpwm1 *1*
500000 0>; ?
On 10/3/19 9:44 AM, Mark A. Yoder wrote:
Drew, David:
I've adapted the tinyDRM dtc to work with the Adafruit 2.4" TFT LCD
display. It's working fine with SPI 1. Currently it uses P9_14 for the backlight.
How do I switch it to use P9_16 for the backlight?
I've tried changing all the P9_14's to P9_16s, but that doesn't work.
P9_14 is the A side of the pwm
and P9_16 is the B side, so I think there's a bit I need to flip, but don't
know what it is.
--Mark
p.s. The exercise for my students will be to switch it to SPI 0!
[1]
https://github.com/MarkAYoder/BeagleBoard-exercises/tree/master/displays/ili9341/tinyDRM
<https://github.com/MarkAYoder/BeagleBoard-exercises/tree/master/displays/ili9341/tinyDRM>
On Thursday, February 22, 2018 at 4:27:10 AM UTC-5, Drew Fustini wrote:
fyi - I've created a bb.org-overlays pull request to add an overlay
named BB-LCD-ADAFRUIT-18-SPI1-00A0.dts for the Adafruit 1.8" LCD on
SPI1:
https://github.com/beagleboard/bb.org-overlays/pull/68
<https://github.com/beagleboard/bb.org-overlays/pull/68>
On Wed, Feb 21, 2018 at 11:34 PM, Drew Fustini <dr...@beagleboard.org>
wrote:
> Thanks! I had DC and Reset swapped in the overlay file. I've fixed
and the
> display is now working! The console is displayed after bootup and
libdrm
> modetest is able to display color bars OK.
>
> Here is the updated dts:
> https://gist.github.com/pdp7/aee5664598059c9b9a9020f107957f80
<https://gist.github.com/pdp7/aee5664598059c9b9a9020f107957f80>
>
> Thanks,
> Drew
>
> On Feb 21, 2018 1:53 PM, "David Lechner" <da...@lechnology.com> wrote:
>>
>> On 02/21/2018 01:18 PM, Drew Fustini wrote:
>>>
>>> On Wed, Feb 21, 2018 at 11:01 AM, David Lechner
<da...@lechnology.com>
>>> wrote:
>>>>
>>>> Are you sure your phandles are correct here? They don't match the
>>>> comments.
>>>> Should it be <&gpio1 16 0> instead?
>>>>
>>>>> + reset-gpios = <&gpio1 16 0>; /*
>>>>> reset:60 P9.12 GPIO1_28 */
>>>>
>>>>
>>>> And then <&gpio1 28 0> here?
>>>
>>> Here is the full BB-SPIDEV1-00A0.dts:
>>> https://gist.github.com/pdp7/aee5664598059c9b9a9020f107957f80
<https://gist.github.com/pdp7/aee5664598059c9b9a9020f107957f80>
>>>
>>> I have P9.12 connected to LCD reset pin. I have P9.15 connected to
>>> LCD dc pin. For fbtft driver, this translated to GPIO_60 for reset
>>> and GPIO_48 for dc. This is based on this pinout diagram:
>>> https://elinux.org/File:Cape_expansion_headers.PNG
<https://elinux.org/File:Cape_expansion_headers.PNG>
>>>
>>> For this dts file, I was trying to figure out what appropriate gpio
>>> phandle. I looked at this table for the P9 header:
>>> https://elinux.org/File:H9Pinout.PNG
<https://elinux.org/File:H9Pinout.PNG>
>>>
>>> I believe that gpio1[16] corresponds to P9.15 which is LCD dc pin,
and
>>> gpio1[28] corresponds to P9.12 which is LCD reset pin.
>>>
>>> My understanding of those mappings may be incorrect, so I'd
appreciate
>>> any additional feedback.
>>>
>> You understand correct, but I think you have swapped the values in
your
>> device tree overlay. You say "gpio1[16] corresponds to P9.15 which
is LCD dc
>> pin", but in the overlay, you have dc-gpios = <&gpio1 28 0>;.
Likewise
>> "gpio1[28] corresponds to P9.12 which is LCD reset pin.", but you
have
>> reset-gpios = <&gpio1 16 0>;.
>>
>>
>
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