samples: display: add a simple sample for st7789v display

This adds a basic app which puts some rectangles on the display

It's hard to write an equivalent README to the rest of the sample
documentation, as the LCD I have uses a custom board thrown together for
testing. (ie other LCDs have publicly available modules)

Signed-off-by: Marc Reilly <marc@cpdesign.com.au>

samples/display/st7789v/CMakeLists.txt

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+# SPDX-License-Identifier: Apache-2.0
+
+cmake_minimum_required(VERSION 3.13.1)
+include($ENV{ZEPHYR_BASE}/cmake/app/boilerplate.cmake NO_POLICY_SCOPE)
+project(st7789v)
+
+target_sources(app PRIVATE src/main.c)

samples/display/st7789v/README.rst

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+.. _st7789v-sample:
+
+ST7789V Display driver
+######################
+
+Overview
+********
+This sample will draw some basic rectangles onto the display.
+The rectangle colors and positions are chosen so that you can check the
+orientation of the LCD and correct RGB bit order. The rectangles are drawn
+in clockwise order, from top left corner: Red, Green, Blue, grey. The shade of
+grey changes from black through to white. (if the grey looks too green or red
+at any point then the LCD may be endian swapped).
+
+Note: The display driver rotates the display so that the 'natural' LCD
+orientation is effectively 270 degrees clockwise of the default display
+controller orientation.
+
+Building and Running
+********************
+The sample has a board overlay for a nrf52832 based board with the following
+pin assignments:
+
++-------------+-------------+
+| | nRF52832  | | LCD module|
+| | Pin       | | signal    |
++=============+=============+
+| P0.03       | SPI_SCK     |
++-------------+-------------+
+| P0.05       | SPI_MOSI    |
++-------------+-------------+
+| P0.26       | SPI_MISO    |
++-------------+-------------+
+| P0.27       | CS          |
++-------------+-------------+
+| P0.25       | DATA/CMD    |
++-------------+-------------+
+| P0.02       | RESET       |
++-------------+-------------+
+
+You might need to alter these according to your specific board/LCD configuration.
+
+For :ref:`nrf52_pca10040`, build this sample application with the following commands:
+
+.. zephyr-app-commands::
+   :zephyr-app: samples/display/st7789v
+   :board: nrf52_pca10040
+   :goals: build
+   :compact:
+
+See :ref:`nrf52_pca10040` on how to flash the build.
+
+
+References
+**********
+
+- `ST7789V datasheet`_
+
+.. _Manufacturer site: https://www.sitronix.com.tw/en/product/Driver/mobile_display.html
+.. _ST7789V datasheet: https://www.crystalfontz.com/controllers/Sitronix/ST7789V/

samples/display/st7789v/nrf52_pca10040.overlay

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+/*
+ * Copyright (c) 2019 Creative Product Design
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+&spi0 {
+	status = "okay";
+	sck-pin = <3>;
+	mosi-pin = <5>;
+	miso-pin = <26>;
+	cs-gpios = <&gpio0 27 0>;
+
+	st7789v@0 {
+		compatible = "sitronix,st7789v";
+		label = "DISPLAY";
+		spi-max-frequency = <20000000>;
+		reg = <0>;
+		cmd-data-gpios = <&gpio0 25 0>;
+		reset-gpios = <&gpio0 2 0>;
+		width = <320>;
+		height = <170>;
+		y-offset = <35>;
+	};
+};

samples/display/st7789v/prj.conf

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+CONFIG_PRINTK=y
+
+CONFIG_HEAP_MEM_POOL_SIZE=16384
+
+CONFIG_GPIO=y
+CONFIG_SPI=y
+
+CONFIG_DISPLAY=y
+CONFIG_ST7789V=y
+CONFIG_ST7789V_LCD_TL019FQV01=y
+CONFIG_ST7789V_RGB565=y
+
+CONFIG_DISPLAY_LOG_LEVEL_DBG=y
+
+CONFIG_LOG=y

samples/display/st7789v/sample.yaml

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+sample:
+  description: Sample application for ST7789V display
+  name: st7789v_sample
+tests:
+  sample.display.st7789v:
+    build_only: true
+    platform_whitelist: nrf52_pca10040
+    tags: display

samples/display/st7789v/src/main.c

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+/*
+ * Copyright (c) 2019 Marc Reilly
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+#include <logging/log.h>
+LOG_MODULE_REGISTER(app, LOG_LEVEL_INF);
+
+#include <zephyr.h>
+#include <device.h>
+#include <display.h>
+
+static void backlight_init(void)
+{
+    /* If you have a backlight, set it up and turn it on here */
+}
+
+void main(void)
+{
+	LOG_INF("ST7789V display sample");
+	struct device *display_dev;
+
+	struct display_capabilities capabilities;
+	struct display_buffer_descriptor buf_desc;
+
+	backlight_init();
+
+#ifdef CONFIG_ST7789V_RGB565
+	const size_t rgb_size = 2;
+#else
+	const size_t rgb_size = 3;
+#endif
+
+	display_dev = device_get_binding(DT_INST_0_SITRONIX_ST7789V_LABEL);
+
+	if (display_dev == NULL) {
+		LOG_ERR("Device not found. Aborting test.");
+		return;
+	}
+
+	display_get_capabilities(display_dev, &capabilities);
+
+	/* size of the rectangle */
+	const size_t w = 40;
+	const size_t h = 20;
+	const size_t buf_size = rgb_size * w * h;
+
+	/* points are clockwise, from top left */
+	size_t x0, y0, x1, y1, x2, y2, x3, y3;
+
+	/* top left */
+	x0 = 0;
+	y0 = 0;
+	/* top right */
+	x1 = capabilities.x_resolution - w;
+	y1 = 0;
+	/* bottom right */
+	x2 = capabilities.x_resolution - w;
+	y2 = capabilities.y_resolution - h;
+	/* bottom left */
+	x3 = 0;
+	y3 = capabilities.y_resolution - h;
+
+	/* Allocate rectangular buffer for corner data */
+	u8_t *buf = k_malloc(buf_size);
+
+	if (buf == NULL) {
+		LOG_ERR("Could not allocate memory. Aborting test.");
+		return;
+	}
+
+	/* Clear frame buffer before enabling LCD, reuse corner buffer
+	 */
+	int h_step;
+	(void)memset(buf, 0, buf_size);
+	h_step = (w * h) / capabilities.x_resolution;
+
+	buf_desc.buf_size = buf_size;
+	buf_desc.pitch = capabilities.x_resolution;
+	buf_desc.width = capabilities.x_resolution;
+	buf_desc.height = h_step;
+
+	for (int idx = 0; idx < capabilities.y_resolution; idx += h_step) {
+		display_write(display_dev, 0, idx, &buf_desc,  buf);
+	}
+
+	display_blanking_off(display_dev);
+
+	buf_desc.pitch = w;
+	buf_desc.width = w;
+	buf_desc.height = h;
+
+	int grey_count = 0;
+	size_t cnt = 0;
+
+	while (1) {
+		/* Update the color of the rectangle buffer and write the buffer
+		 * to  one of the corners
+		 */
+#ifdef CONFIG_ST7789V_RGB565
+		int color = cnt % 4;
+		/* RGB565 format */
+		u16_t color_r;
+		u16_t color_g;
+		u16_t color_b;
+		u16_t color_rgb;
+
+		color_r = (color == 0) ? 0xF800U : 0U;
+		color_g = (color == 1) ? 0x07E0U : 0U;
+		color_b = (color == 2) ? 0x001FU : 0U;
+		color_rgb = color_r + color_g + color_b;
+		if (color == 3) {
+			u16_t t = grey_count & 0x1f;
+			/* shift the green an extra bit, it has 6 bits */
+			color_rgb = t << 11 | t << (5+1) | t;
+			grey_count++;
+		}
+
+		for (size_t idx = 0; idx < buf_size; idx += rgb_size) {
+			*(buf + idx + 0) = (color_rgb >> 8) & 0xFFU;
+			*(buf + idx + 1) = (color_rgb >> 0) & 0xFFU;
+		}
+#else
+		u32_t color_rgb;
+		u32_t c = grey_count & 0xff;
+
+		switch (cnt % 4) {
+		case 0:
+			color_rgb = 0x00FF0000u;
+			break;
+		case 1:
+			color_rgb = 0x0000FF00u;
+			break;
+		case 2:
+			color_rgb = 0x000000FFu;
+			break;
+		case 3:
+			color_rgb = c << 16 | c << 8 | c;
+			grey_count++;
+			break;
+		}
+
+		/* RGB888 format */
+		for (size_t idx = color; idx < buf_size; idx += rgb_size) {
+			*(buf + idx + 0) = color_rgb >> 16;
+			*(buf + idx + 1) = color_rgb >> 8;
+			*(buf + idx + 2) = color_rgb >> 0;
+		}
+#endif
+
+		switch (cnt % 4) {
+		case 0:
+			/* top left, red */
+			display_write(display_dev, x0, y0, &buf_desc, buf);
+			break;
+		case 1:
+			/* top right, green */
+			display_write(display_dev, x1, y1, &buf_desc, buf);
+			break;
+		case 2:
+			/* bottom right, blue */
+			display_write(display_dev, x2, y2, &buf_desc, buf);
+			break;
+		case 3:
+			/* bottom left, alternating grey */
+			display_write(display_dev, x3, y3, &buf_desc, buf);
+			break;
+		}
+		++cnt;
+		k_sleep(100);
+	}
+}