炬芯原廠linux開發(fā)actduino使用gpio模擬

1、版本號：1. 02015-07-251 目錄12錄1言2編寫目的2術語和縮寫詞2目引2.12.234567添加dts3內(nèi)核配置4測試4版本歷史6.7第 1 頁2 引言2.1 編寫目的對于 I2C 不夠用、或速度比較低的特殊場合，有時需要使用 GPIO 來模擬 i2c。目前 Linux內(nèi)核已經(jīng)做了很好的支持，bitbanging（/drivers/i2c/busses/i2c-gpio.c）主要來完成模式 i2c 功能，對此開發(fā)無需再專門寫個驅(qū)動。本文基于 S500介紹供開發(fā)者參考。2.2術語和縮寫詞第 2 頁縮寫和術語解 釋dtsDevice Tree Source，目標板硬件信息3 添加 d

2、tsBitbanging 已經(jīng)實現(xiàn)了 dts 與 platform_data兩種方式，具體查看 i2c-gpio.c 中的i2c_gpio_probe 函數(shù)，dts 相對比較簡單，無需修改board 文件，這里以 dts 為例，有興趣的可研究下 platform_data。針對 dts 方式，只需要對應板型的 dts 中添加如下部分：第 3 頁i2c0 /*字符串不能修改，具體見 i2c-gpio.c 中的 i2c_gpio_dt_ids。*如需修改，兩邊 compatible 字段保持同步。*/compatible = i2c-gpio;/*gpio 配置，第一個 gpio 描述 sda,第

3、二個是 scl，別反了*/ gpios = ;/*開漏極配置，其并不是真正的把 gpio 設為開漏極，僅僅是*sda/scl 設為 high。*/i2c-gpio,spen-drain; i2c-gpio,scl-open-drain;/*clk 周期設置*/i2c-gpay-us = ;/* 100 kHz */ #address-cells = ;#size-cells = ;/測試代碼的配置，與標準 i2c 設備配置相同i2cdev50compatible =actions,i2cdev; reg = ;4 內(nèi)核配置默認內(nèi)核是沒打開，需要手動打開：makeconfig或直接修改對應板型的

4、 deconfig 文件，如 kernel/arch/arm/configs/atm7059a_s500_defconfig5 測試完成以上操作，編譯并替換 dtb 與 uImage 文件，使用 i2c_owl_dev.ko 或其它 i2c 測試用例，用示波器測試 sda 與 scl 兩個pin 的波形：第 4 頁# CONFIG_I2C_GPIO is not set修改為： CONFIG_I2C_GPIO=yDevice Drivers- I2C support-I2C Hardware Bupport- GPIO-based bitbanging I2C第 5 頁6 版本歷史第 6 頁日

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