v3s点不亮framebuffer st7735r，之reset被拉低。

casdfxx2025-12-08 8:13

一、先写下解决方法，debug过程就当做乐子给大家看吧。

问题原因：

reset顺序颠倒。

解决方法：

static void fbtft_reset(struct fbtft_par *par)里，将

gpiod_set_value_cansleep(1)

gpiod_set_value_cansleep(0)

修改为

gpiod_set_value_cansleep(0)

gpiod_set_value_cansleep(1)

一些参考链接，但是不是我遇到的问题

全志v851s使用fbtft驱动0.96寸st7735屏分享 | 全志在线开发者论坛

求助荔枝派zero 驱动st7735 0.96寸spi屏幕 / 全志 SOC / WhyCan Forum(哇酷开发者社区)

用户态fbset上看也没问题：

二、尝试从硬件/pull up上解决

问题现入僵局，从软件上看一切正常，但是st7735是没有输出的，芯片也看不到是否运行正常。所以拿出示波器，看到reset脚一直是拉低的。

检查原理图：

网上都在说reset，dc要加上拉之类的。我没有加，难道是因为没有配置成上拉模式吗？（其实这里被网络上带偏了，后来才发现）。那么是加上拉有两种方式：

1、通过硬件的方式，因为拉测试点时，已经将reset信号拉出，只需要接到按键的上拉电阻就完事。

2、通过软件配置PE6，也就是reset脚为上拉输出。（万一配置成了开漏，或都弱输出也是会影响信号的。那样再改回来就行）。

想着按方法一，但是最后还是要要改软件。而且方法一一定可行，不需要再试了。就打算用方法二，其实电烙铁已经准备好了，就是不想动手焊来回跑。

修改设备树sun8i-v3s.dtsi，在pio下添加：

cpp 复制代码 
tft_lcd_pins: tft-lcd-pins {
				pins = "PE5", "PE6";
				function = "gpio_out";
				bias-pull-up;
			};

修改设备树sun8i-v3s-licheepi-zero-with-st7735-lcd.dts：

cpp 复制代码 
pinctrl-names = "default";
		pinctrl-0 = <&tft_lcd_pins>;
		dc-gpios = <&pio 4 5 GPIO_ACTIVE_HIGH>; // PE5
		reset-gpios = <&pio 4 6 GPIO_ACTIVE_LOW>; // PE6

结果pinctrl-0 = <&tft_lcd_pins>;与

dc-gpios = <&pio 4 5 GPIO_ACTIVE_HIGH>; // PE5

reset-gpios = <&pio 4 6 GPIO_ACTIVE_LOW>; // PE6

冲突了，重复request 同一个gpio。

相关问题可以看我的另一篇文章：

V3s pinctrl与gpio的耦合问题

3、于是换一种方法，手动设置pe6为上拉：

cpp 复制代码 
static int fbtft_request_gpios(struct fbtft_par *par)
{
	int i;
	int ret;
	int* temp; 
	int* config;
	int* driver;
	int gpio_pin_num;

	ret = fbtft_request_one_gpio(par, "reset-gpios", 0, &par->gpio.reset);
	if (ret)
		return ret;
	
		
	gpio_pin_num		= 6;
	temp                = (int*)(0x1c20800 + 4*0x24 + 0x1c + gpio_pin_num/16*4);
	temp                = ioremap(temp, 4);

	config				= (int*)(0x1c20800 + 0x90);
	config              = ioremap(config, 4);

	driver				= (int*)(0x1c20800 + 0xA4);
	driver              = ioremap(driver, 4);
	//*driver				|= 3<12;

	printk("[test] (config:%x) (driver:%x) (pull:%x) \n", *config, *driver, *temp);
	*temp               &= ~(3<<(12));
	*temp               |= 1<<(12);//1:pull_up, 2:pull_down.
	iounmap(temp);
	iounmap(config);
	iounmap(driver);

	ret = fbtft_request_one_gpio(par, "dc-gpios", 0, &par->gpio.dc);
	if (ret)
		return ret;
	ret = fbtft_request_one_gpio(par, "rd-gpios", 0, &par->gpio.rd);
	if (ret)
		return ret;
	ret = fbtft_request_one_gpio(par, "wr-gpios", 0, &par->gpio.wr);
	if (ret)
		return ret;
	ret = fbtft_request_one_gpio(par, "cs-gpios", 0, &par->gpio.cs);
	if (ret)
		return ret;
	ret = fbtft_request_one_gpio(par, "latch-gpios", 0, &par->gpio.latch);
	if (ret)
		return ret;
	for (i = 0; i < 16; i++) {
		ret = fbtft_request_one_gpio(par, "db-gpios", i,
					     &par->gpio.db[i]);
		if (ret)
			return ret;
		ret = fbtft_request_one_gpio(par, "led-gpios", i,
					     &par->gpio.led[i]);
		if (ret)
			return ret;
		ret = fbtft_request_one_gpio(par, "aux-gpios", i,
					     &par->gpio.aux[i]);
		if (ret)
			return ret;
	}

	return 0;
}

打印出来看到的值为0 ( test (*pe6:0) )

复制代码 
063647] usbcore: registered new interface driver usbhid
[    1.069537] usbhid: USB HID core driver
[    1.073638] fb_st7735r spi0.0: fbtft_property_value: buswidth = 8
[    1.079846] fb_st7735r spi0.0: fbtft_property_value: debug = 0
[    1.085724] fb_st7735r spi0.0: fbtft_property_value: rotate = 0
[    1.091653] fb_st7735r spi0.0: fbtft_property_value: fps = 30
[    1.098082] sun8i-v3s-pinctrl 1c20800.pinctrl: supply vcc-pe not found, using dummy regulator
[    1.107132] fb_st7735r spi0.0: success to request reset-gpios GPIO134
[    1.113700] [test] (*pe6:0)
[    1.116842] sunxi-mmc 1c0f000.mmc: initialized, max. request size: 16384 KB
[    1.124515] fb_st7735r spi0.0: success to request dc-gpios GPIO133
[    1.165638] mmc0: host does not support reading read-only switch, assuming write-enable
[    1.175753] mmc0: new high speed SD card at address 211d
[    1.183312] mmcblk0: mmc0:211d APPSD 1.88 GiB
[    1.193116]  mmcblk0: p1 p2
[    2.110583] graphics fb0: fb_st7735r frame buffer, 128x160, 40 KiB video memory, 4 KiB buffer memory, fps=33, spi0.0 at 4 MHz
[    2.126134] Initializing XFRM netlink socket
还是不行，继续添加 config，driver，pull后，打印出信息：
复制代码 
] usbhid: USB HID core driver
[    1.070207] fb_st7735r spi0.0: fbtft_property_value: buswidth = 8
[    1.076414] fb_st7735r spi0.0: fbtft_property_value: debug = 0
[    1.082261] fb_st7735r spi0.0: fbtft_property_value: rotate = 0
[    1.088215] fb_st7735r spi0.0: fbtft_property_value: fps = 30
[    1.094754] sun8i-v3s-pinctrl 1c20800.pinctrl: supply vcc-pe not found, using dummy regulator
[    1.103647] fb_st7735r spi0.0: success to request reset-gpios GPIO134
[    1.110326] [test] (config:71777777) (driver:55555555) (pull:0)
[    1.116568] sunxi-mmc 1c0f000.mmc: initialized, max. request size: 16384 KB
[    1.124018] fb_st7735r spi0.0: success to request dc-gpios GPIO133
[    1.165202] mmc0: host does not support reading read-only switch, assuming write-enable
[    1.175321] mmc0: new high speed SD card at address 211d
[    1.182869] mmcblk0: mmc0:211d APPSD 1.88 GiB
[    1.192652]  mmcblk0: p1 p2
[    2.110803] graphics fb0: fb_st7735r frame buffer, 128x160, 40 KiB video memory, 4 KiB buffer memory, fps=33, spi0.0 at 4 MHz
[    2.126320] Initializing XFRM netlink socket

test (config:71777777) (driver:55555555) (pull:0)

0x71就是pe6配置为output

0x5就是0101，就是level1

pull就是disable。

5、找到问题原因

看配置也没有问题。把屏幕去掉，重新启动，看到现象和以前一样。那么就不是驱动能力这些电器属性造成的。

如图，黄色是reset，蓝色是dc。

看波形reset是被软件拉低了，然后一直没有恢复。下面就是分析fb_st7735r.c的初始化过程了。

============================st7735r初始化过程============================

fbtft_framebuffer_alloc

fbops->owner = dev->driver->owner;

fbops->fb_read = fb_sys_read;

fbops->fb_write = fbtft_fb_write;

fbops->fb_fillrect = fbtft_fb_fillrect;

fbops->fb_copyarea = fbtft_fb_copyarea;

fbops->fb_imageblit = fbtft_fb_imageblit;

fbops->fb_setcolreg = fbtft_fb_setcolreg;

fbops->fb_blank = fbtft_fb_blank;

/* default fbtft operations */

par->fbtftops.write = fbtft_write_spi;

par->fbtftops.read = fbtft_read_spi;

par->fbtftops.write_vmem = fbtft_write_vmem16_bus8;

par->fbtftops.write_register = fbtft_write_reg8_bus8;

par->fbtftops.set_addr_win = fbtft_set_addr_win;

par->fbtftops.reset = fbtft_reset;

par->fbtftops.mkdirty = fbtft_mkdirty;

par->fbtftops.update_display = fbtft_update_display;

if (display->backlight)

par->fbtftops.register_backlight = fbtft_register_backlight;

fbtft_reset() 发现该函数是这样写的：

cpp 复制代码 
static void fbtft_reset(struct fbtft_par *par)
{
	if (!par->gpio.reset)
		return;

	fbtft_par_dbg(DEBUG_RESET, par, "%s()\n", __func__);

	gpiod_set_value_cansleep(par->gpio.reset, 1);
	usleep_range(20, 40);
	gpiod_set_value_cansleep(par->gpio.reset, 0);
	msleep(120);

	gpiod_set_value_cansleep(par->gpio.cs, 1);  /* Activate chip */
}

字面意思是reset脚先置高，等一段时间后，再置低。

st7735我太熟悉了，正常启动流程正好相反，是先将reset拉低，再拉高。因为离开函数前，是手动设置为低，所以符合之前看到的波形。

所以修改为：

cpp 复制代码 
static void fbtft_reset(struct fbtft_par *par)
{
	if (!par->gpio.reset)
		return;

	fbtft_par_dbg(DEBUG_RESET, par, "%s()\n", __func__);

	//gpiod_set_value_cansleep(par->gpio.reset, 1);
	gpiod_set_value_cansleep(par->gpio.reset, 0);
	usleep_range(20, 40);
	//gpiod_set_value_cansleep(par->gpio.reset, 0);
	gpiod_set_value_cansleep(par->gpio.reset, 1);
	msleep(120);

	gpiod_set_value_cansleep(par->gpio.cs, 1);  /* Activate chip */
}

获得波形如下（可以看到reset信号已经正常了）：

输入以下命令：

dd if=urandom of=fb0 bs=1k count=40

可得图片：

看到从黑屏，刷到了随机点。这样一来，一切都正常了。

=======================================================================

三、修改显示偏移

什么，你说屏幕有白边，那就改这里：

cpp 复制代码 
#define X_OFFSET	(1U)
#define Y_OFFSET	(2U)
static void set_addr_win(struct fbtft_par *par, int xs, int ys, int xe, int ye)
{
	xs	+= X_OFFSET;xe	+= X_OFFSET;
	ys	+= Y_OFFSET;ye	+= Y_OFFSET;

	write_reg(par, MIPI_DCS_SET_COLUMN_ADDRESS,
		  xs >> 8, xs & 0xFF, xe >> 8, xe & 0xFF);

	write_reg(par, MIPI_DCS_SET_PAGE_ADDRESS,
		  ys >> 8, ys & 0xFF, ye >> 8, ye & 0xFF);

	write_reg(par, MIPI_DCS_WRITE_MEMORY_START);
}

四、设备树备份：

复制代码 
/*
 * Copyright (C) 2016 Icenowy Zheng <icenowy@aosc.xyz>
 *
 * This file is dual-licensed: you can use it either under the terms
 * of the GPL or the X11 license, at your option. Note that this dual
 * licensing only applies to this file, and not this project as a
 * whole.
 *
 *  a) This file is free software; you can redistribute it and/or
 *     modify it under the terms of the GNU General Public License as
 *     published by the Free Software Foundation; either version 2 of the
 *     License, or (at your option) any later version.
 *
 *     This file is distributed in the hope that it will be useful,
 *     but WITHOUT ANY WARRANTY; without even the implied warranty of
 *     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *     GNU General Public License for more details.
 *
 * Or, alternatively,
 *
 *  b) Permission is hereby granted, free of charge, to any person
 *     obtaining a copy of this software and associated documentation
 *     files (the "Software"), to deal in the Software without
 *     restriction, including without limitation the rights to use,
 *     copy, modify, merge, publish, distribute, sublicense, and/or
 *     sell copies of the Software, and to permit persons to whom the
 *     Software is furnished to do so, subject to the following
 *     conditions:
 *
 *     The above copyright notice and this permission notice shall be
 *     included in all copies or substantial portions of the Software.
 *
 *     THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 *     EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
 *     OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 *     NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
 *     HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
 *     WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 *     FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
 *     OTHER DEALINGS IN THE SOFTWARE.
 */

/dts-v1/;
#include "sun8i-v3s.dtsi"
#include "sunxi-common-regulators.dtsi"

/ {
	model = "Lichee Pi Zero";
	compatible = "licheepi,licheepi-zero", "allwinner,sun8i-v3s";

	aliases {
		serial0 = &uart0;
		serial2 = &uart2;
	};

	chosen {
		stdout-path = "serial2:115200n8";
	};
};

&mmc0 {
	broken-cd;
	bus-width = <4>;
	vmmc-supply = <&reg_vcc3v3>;
	status = "okay";
};

&uart0 {
	pinctrl-0 = <&uart0_pb_pins>;
	pinctrl-names = "default";
	status = "okay";
};

&uart2 {
	pinctrl-0 = <&uart2_pb_pins>;
	pinctrl-names = "default";
	status = "okay";
};

&usb_otg {
	dr_mode = "otg";
	status = "okay";
};

&usbphy {
	usb0_id_det-gpios = <&pio 5 6 GPIO_ACTIVE_HIGH>;
	status = "okay";
};

&codec {
        allwinner,audio-routing =
                "Headphone", "HP",
                "Headphone", "HPCOM",
                "MIC1", "Mic",
                "Mic",  "HBIAS";
        status = "okay";
};

&ohci0 {
        status = "okay";
};
&ehci0 {
        status = "okay";
};


&spi0 {
	status = "okay";
	pinctrl-names = "default";
	pinctrl-0 = <&spi0_pins>;
	cs-gpios = <0>;

	st7735r@0{
		compatible = "sitronix,st7735r";
		reg = <0x0>;
		status = "okay";
		spi-max-frequency = <48000000>;
		spi-cpol;
		spi-cpha; 
		fps = <60>;
		buswidth = <8>;
		//pinctrl-names = "default";
		//pinctrl-0 = <&tft_lcd_pins>;
		dc-gpios = <&pio 4 5 GPIO_ACTIVE_HIGH>; // PE5
		reset-gpios = <&pio 4 6 GPIO_ACTIVE_LOW>; // PE6


		debug = <0x0>;
		rotate = <90>;
	};
};
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