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電子工程網

標題: 全志A40i開發板PWM 的應用 [打印本頁]

作者: 哦哈喲 時間: 2021-11-18 16:28
標題: 全志A40i開發板PWM 的應用

本文講解了國產A40i 開發板PWM的應用，本篇文章主要適用于飛凌 OKA40i 平臺Linux3.10.65 操作系統，其他arm 平臺也可以參考，但是不同平臺之間會存在差異，請自行修改以適應自己的使用。寫本文章的主要目的是協助客戶加速產品的研發速度，由于水平有限，不提供任何的完整性、可靠性等保證，軟件版本更新之后，有些位置名稱等內容可能會及時更新，修改方法請參考使用。

一、PWM的應用1、pwm的添加

增加一路 pwm，以 pwm4 為例說明，其他方法類似，只做為參考。

arch/arm/boot/dts/sun8iw11p1.dtsi

中添加

pwm = &pwm;pwm0 = &pwm0;pwm4 = &pwm4;
pwm: pwm@01c23400 {       compatible = "allwinner,sunxi-pwm";
      reg = <0x0 0x01c23400 0x0 0x154>;
   pwm-number = <1>;
      pwm-base = <0x4>;
      pwms = <&pwm4>;
};pwm4: pwm4@01c23400 {       compatible = "allwinner,sunxi-pwm4";
      pinctrl-names = "active", "sleep";
      reg_base = <0x01c23400>;
      reg_peci_offset = <0x00>;
      reg_peci_shift = <0x04>;
      reg_peci_width = <0x01>;
      reg_pis_offset = <0x04>;
   reg_pis_shift = <0x04>;
   reg_pis_width = <0x01>;
   reg_crie_offset = <0x10>;
      reg_crie_shift = <0x08>;
      reg_crie_width = <0x01>;
   reg_cfie_offset = <0x10>;
   reg_cfie_shift = <0x09>;
      reg_cfie_width = <0x01>;
   reg_cris_offset = <0x14>;
      reg_cris_shift = <0x08>;
      reg_cris_width = <0x01>;
      reg_cfis_offset = <0x14>;
   reg_cfis_shift = <0x09>;
      reg_cfis_width = <0x01>;
      reg_clk_src_offset = <0x28>;
      reg_clk_src_shift = <0x07>;
      reg_clk_src_width = <0x02>;
      reg_bypass_offset = <0x28>;
      reg_bypass_shift = <0x05>;
      reg_bypass_width = <0x01>;
      reg_clk_gating_offset = <0x28>;
      reg_clk_gating_shift = <0x04>;
      reg_clk_gating_width = <0x01>;
      reg_clk_div_m_offset = <0x28>;
      reg_clk_div_m_shift = <0x00>;
      reg_clk_div_m_width = <0x04>;
      reg_pdzintv_offset = <0x38>;
      reg_pdzintv_shift = <0x08>;
      reg_pdzintv_width = <0x08>;
      reg_dz_en_offset = <0x38>;
      reg_dz_en_shift = <0x00>;
      reg_dz_en_width = <0x01>;
      reg_enable_offset = <0x40>;
      reg_enable_shift = <0x04>;
      reg_enable_width = <0x01>;
      reg_cap_en_offset = <0x44>;
      reg_cap_en_shift = <0x04>;
      reg_cap_en_width = <0x01>;
      reg_period_rdy_offset = <0xe0>;
      reg_period_rdy_shift = <0x0b>;
   reg_period_rdy_width = <0x01>;
      reg_pul_start_offset = <0xe0>;
      reg_pul_start_shift = <0x0a>;
      reg_pul_start_width = <0x01>;
      reg_mode_offset = <0xe0>;
   reg_mode_shift = <0x09>;
      reg_mode_width = <0x01>;
      reg_act_sta_offset = <0xe0>;
      reg_act_sta_shift = <0x08>;
      reg_act_sta_width = <0x01>;
      reg_prescal_offset = <0xe0>;
      reg_prescal_shift = <0x00>;
      reg_prescal_width = <0x08>;
      reg_entire_offset = <0xe4>;
      reg_entire_shift = <0x10>;
      reg_entire_width = <0x10>;
      reg_active_offset = <0xe4>;
      reg_active_shift = <0x00>;
      reg_active_width = <0x10>; }

按手冊 PWM 修改對應的寄存器。

修改 sys_config.fex 中 twi2_used=0 且增加

[pwm4]pwm_used = 1pwm_positive = port

B20<4><0>[pwm4_suspend]pwm_positive = port

B20<7><0>

編譯鏡像并燒寫

2、PWM的測試
echo 0 >/sys/class/pwm/pwmchip4/exportecho 1000000 > /sys/class/pwm/pwmchip4/pwm0/periodecho 500000 > /sys/class/pwm/pwmchip4/pwm0/duty_cycleecho 1 > /sys/class/pwm/pwmchip4/pwm0/enable

測量得到頻率為 1K 方波

echo 0 > /sys/class/pwm/pwmchip4/pwm0/enableecho 208333> /sys/class/pwm/pwmchip4/pwm0/duty_cycleecho 416667 > /sys/class/pwm/pwmchip4/pwm0/periodecho 1 > /sys/class/pwm/pwmchip4/pwm0/enable

測量得到頻率為 2.4K 方波

原文鏈接：https://www.forlinx.com/article_view_784.html

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