全志A40i开发板PWM 的应用-飞凌国产芯片系列干货

祢豆子

本文讲解了国产[color=inherit !important]A40i [color=inherit !important]开发板PWM的应用，本篇文章主要适用于[color=inherit !important]飞凌 OKA40i 平台 [color=inherit !important]Linux3.10.65 操作系统，其他ARM 平台也可以参考，但是不同平台之间会存在差异，请自行修改以适应自己的使用。 写本文章的主要目的是协助客户加速产品的研发速度，由于水平有限， 不提供任何的完整性、可靠性等保证，软件版本更新之后，有些位置名称等内容可能会及时更新，修改方法请参考使用。

一、PWM的应用1、pwm的添加

增加一路 pwm，以 pwm4 为例说明，其他方法类似，只做为参考。

arch/arm/boot/dts/sun8iw11p1.dtsi
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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>; }
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按手册 PWM 修改对应的寄存器。

修改 sys_config.fex 中 twi2_used=0 且增加

% L8 m% V5 M3 L8 R2 I" Y[pwm4]pwm_used = 1pwm_positive = portB20<4><0><default><default>[pwm4_suspend]pwm_positive = portB20<7><0><default><default>

编译镜像并烧写

2、PWM的测试
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
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测量得到频率为 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
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测量得到频率为 2.[color=inherit !important]4K 方波

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MLXG

PWM测试的方法是什么