炬芯原厂linux开发actduino使用gpio模拟

1、版本号：1. 02015-07-251 目录12录1言2编写目的2术语和缩写词2目引2.12.234567添加dts3内核配置4测试4版本历史6.7第 1 页2 引言2.1 编写目的对于 I2C 不够用、或速度比较低的特殊场合，有时需要使用 GPIO 来模拟 i2c。目前 Linux内核已经做了很好的支持，bitbanging（/drivers/i2c/busses/i2c-gpio.c）主要来完成模式 i2c 功能，对此开发无需再专门写个驱动。本文基于 S500介绍供开发者参考。2.2术语和缩写词第 2 页缩写和术语解 释dtsDevice Tree Source，目标板硬件信息3 添加 d

2、tsBitbanging 已经实现了 dts 与 platform_data两种方式，具体查看 i2c-gpio.c 中的i2c_gpio_probe 函数，dts 相对比较简单，无需修改board 文件，这里以 dts 为例，有兴趣的可研究下 platform_data。针对 dts 方式，只需要对应板型的 dts 中添加如下部分：第 3 页i2c0 /*字符串不能修改，具体见 i2c-gpio.c 中的 i2c_gpio_dt_ids。*如需修改，两边 compatible 字段保持同步。*/compatible = i2c-gpio;/*gpio 配置，第一个 gpio 描述 sda,第

3、二个是 scl，别反了*/ gpios = ;/*开漏极配置，其并不是真正的把 gpio 设为开漏极，仅仅是*sda/scl 设为 high。*/i2c-gpio,spen-drain; i2c-gpio,scl-open-drain;/*clk 周期设置*/i2c-gpay-us = ;/* 100 kHz */ #address-cells = ;#size-cells = ;/测试代码的配置，与标准 i2c 设备配置相同i2cdev50compatible =actions,i2cdev; reg = ;4 内核配置默认内核是没打开，需要手动打开：makeconfig或直接修改对应板型的

4、 deconfig 文件，如 kernel/arch/arm/configs/atm7059a_s500_defconfig5 测试完成以上操作，编译并替换 dtb 与 uImage 文件，使用 i2c_owl_dev.ko 或其它 i2c 测试用例，用示波器测试 sda 与 scl 两个pin 的波形：第 4 页# CONFIG_I2C_GPIO is not set修改为： CONFIG_I2C_GPIO=yDevice Drivers- I2C support-I2C Hardware Bupport- GPIO-based bitbanging I2C第 5 页6 版本历史第 6 页日

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