linux-kernel - Re: [PATCH v3 3/3] drm/tinydrm: add driver for ST7735R panels

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Date:   Sun, 31 Dec 2017 17:19:04 +0100
From:   Noralf Trønnes <noralf@...nnes.org>
To:     David Lechner <david@...hnology.com>,
        dri-devel@...ts.freedesktop.org, devicetree@...r.kernel.org,
        limor@...yada.net
Cc:     Linus Walleij <linus.walleij@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 3/3] drm/tinydrm: add driver for ST7735R panels


Den 21.12.2017 20.35, skrev David Lechner:
> On 12/21/2017 01:23 PM, David Lechner wrote:
>> This adds a new driver for Sitronix ST7735R display panels.
>>
>> This has been tested using an Adafruit 1.8" TFT.
>>
>> Signed-off-by: David Lechner <david@...hnology.com>
>> ---
>
> <snip>
>
>> +    mipi_dbi_command(mipi, ST7735R_GAMCTRP1, 0x0f, 0x1a, 0x0f, 0x18, 
>> 0x2f,
>> +             0x28, 0x20, 0x22, 0x1f, 0x1b, 0x23, 0x37, 0x00, 0x07,
>> +             0x02, 0x10);
>> +    mipi_dbi_command(mipi, ST7735R_GAMCTRN1, 0x0f, 0x1b, 0x0f, 0x17, 
>> 0x33,
>> +             0x2c, 0x29, 0x2e, 0x30, 0x30, 0x39, 0x3f, 0x00, 0x07,
>> +             0x03, 0x10);
> By the way, how do you know what is the "right" gamma curve? I think I 
> copied this from the generic st7735r driver in fbtft, but I noticed 
> that there is also a different curve for the Adafruit 1.8" display in 
> fbtft. I'm wondering if I should have used that one instead. I can't 
> really tell a difference looking at the display.

 From what I can tell this is the curve used by the Arduino library:

https://github.com/adafruit/Adafruit-ST7735-Library/blob/master/Adafruit_ST7735.cpp

static const uint8_t PROGMEM
   Rcmd3[] = {                 // Init for 7735R, part 3 (red or green tab)
     4,                        //  4 commands in list:
     ST7735_GMCTRP1, 16      , //  1: Magical unicorn dust, 16 args, no 
delay:
       0x02, 0x1c, 0x07, 0x12,
       0x37, 0x32, 0x29, 0x2d,
       0x29, 0x25, 0x2B, 0x39,
       0x00, 0x01, 0x03, 0x10,
     ST7735_GMCTRN1, 16      , //  2: Sparkles and rainbows, 16 args, no 
delay:
       0x03, 0x1d, 0x07, 0x06,
       0x2E, 0x2C, 0x29, 0x2D,
       0x2E, 0x2E, 0x37, 0x3F,
       0x00, 0x00, 0x02, 0x10,

void Adafruit_ST7735::initR(uint8_t options) {
   commonInit(Rcmd1);
...
   commandList(Rcmd3);


Noralf.