概述

项目使用树莓派和PCA9685模块连接舵机进行控制，参照pca9685模块手册写了驱动代码，能按照预期进行控制舵机。
记录一下后续回看。

    %PCA9685 此处提供此类的摘要%   初始化输入参数：芯片地址默认（0x40),输出通道(ch),输出频率(freq)%   pwm输出参数：脉宽pulse_widthXCZ范围默认(500us，2500us),输出占空比(0-100)propertiesdevicei2cdevicebus='i2c-1' %设备连接到i2c-1address = '0x40' %设备地址默认0x40freq = 50 % 设置输出频率默认50Hz，周期20ms，最小24Hz，'0xff'，最大1526Hz,'0x03'        duty=0 % 输出占空比delay=0 %无延时endproperties(Access=private)MODE1 = 0x00MODE2 = 0x01SUBADR1 = 0x02SUBADR2 = 0x03SUBADR3 = 0x04ALLCALLADR=0x05LED0_ON_L=0x06LED0_ON_H=0x07LED0_OFF_L=0x08LED0_OFF_H=0x09ALL_LED_ON_L = 0xFAALL_LED_ON_H = 0xFBALL_LED_OFF_L = 0xFCALL_LED_OFF_H = 0xFDPRE_SCALE = 0xFEendpropertiesprecaleval = 25e6alpha=1 %修正系数endmethodsfunction obj = PCA9685(mypi,bus,address)% 构造一个PCA9685对象，类似i2c sensor% 定义i2c地址。obj.device=mypi;obj.i2cdevice=i2cdev(obj.device,bus,address);obj.bus=bus;obj.address = address; endfunction setPWMFreq(obj,value)oldmode=readRegister(obj.i2cdevice,obj.MODE1); % 读MODE1寄存器%检查bit7(RESTART)是1则清空bit4(SLEEP),延时1000usnewmode=bitor(bitand(oldmode,hex2dec('7f')),hex2dec('10'));% SLEEP modewriteRegister(obj.i2cdevice,obj.MODE1,newmode);% set bit4(SLEEP)% tic;% for t=0.001:0.001:1/1000%     while toc<t%     end% end pause(5e-3);%wait 1mswriteRegister(obj.i2cdevice,obj.MODE1,bitor(oldmode,hex2dec('a1')));obj.freq=value;prescale=round(obj.precaleval/(4096*obj.freq*obj.alpha))-1; %计算填入寄存器的值writeRegister(obj.i2cdevice,obj.PRE_SCALE,prescale,'uint16')%填入寄存器newmode=bitset(newmode,5,0); % Normal modewriteRegister(obj.i2cdevice,obj.MODE1,newmode);% 置于正常模式endfunction setAngle(obj,ch,angle)%ch为通道号[0,15]%setPWMDuty(ch,duty)%ch是通道号0-15cycle=1000/obj.freq;min_led_on_time=round(4096/cycle*500e-6);max_led_on_time=round(4096/cycle*2500e-6);led_off_time=min_led_on_time+round((max_led_on_time-min_led_on_time)*angle/180);writeRegister(obj.i2cdevice,obj.LED0_ON_H+ch*4,bitshift(0,-8,"uint16"));writeRegister(obj.i2cdevice,obj.LED0_ON_L+ch*4,bitand(0,hex2dec('ff')));writeRegister(obj.i2cdevice,obj.LED0_OFF_H+ch*4,bitshift(led_off_time,-8,"uint16"));writeRegister(obj.i2cdevice,obj.LED0_OFF_L+ch*4,bitand(led_off_time,hex2dec('ff')));endfunction setPWMDuty(obj,ch,on,off)min_led_on=102;max_led_on=512;if off<min_led_onoff=min_led_on;endif off> max_led_onoff=max_led_on;endwriteRegister(obj.i2cdevice,obj.LED0_ON_H+ch*4,bitshift(on,-8,"uint16"));writeRegister(obj.i2cdevice,obj.LED0_ON_L+ch*4,bitand(on,hex2dec('ff')));writeRegister(obj.i2cdevice,obj.LED0_OFF_H+ch*4,bitshift(off,-8,"uint16"));writeRegister(obj.i2cdevice,obj.LED0_OFF_L+ch*4,bitand(off,hex2dec('ff')));endend
end

树莓派使用mypi=raspi创建，然后可以创建servos=PCA9685(mypi,‘i2c-1’,‘0x40’)，创建一个i2c设备，设备连接能够正常建立，按照舵机使用参考代码，led_off_time的范围理论计算出是104~512，但是实际使用时由于误差，中值设计为300，下限为150，上限为450，能够较好的满足使用需求。