器件：PT2258音量控制器

1 序

  PT2258为台湾普诚电子于2000年7月开发出的由iic总线控制的音量控制IC；音量调节范围[-79,0]dB，调节步长1dB；

2 工作原理

  2.1 工作原理

    PT2258内部集成了可编程电阻网络，通过对Vin进行分压处理后输出Vout，实现音量控制；

    当音量放大倍数为0dB时，Vin=Vout音量最大；当音量放大倍数为-79dB时，Vout音量最小；

  2.2 iic控制

    如图可知pt2258的控制只要通过iic发送3个字节即可；需要注意的是如果ack不为0，需要始终发送stop后重新start开始；

    其中AddressByte的bit[7]=1b，bit[3:2]为[code1:code2]；上图bit[3:2]=10b，所以addr为88h；

3 应用电路

  20pin引脚，12pin输入输出，4pin电源，4pin的iic控制；

  工作电压5-9V，工作电流8mA；Cref=10uF，iic的Tmaxinit =300ms，可能就是pt2258上电稳定时间(page11)；

  pt2258在调节步长的时候有bongbong声是因为在通道和10uF电容之间加了0Ω电阻，替换0Ω电阻为电容就改善了；

4 软件例程

//前4表示通道,后4表示db; datasheet p9; xxxx取值:1001=9,1000=8,...,0001=1,0000=0
#define PT2258_Reg_6CH_1db_STEP        0xE0        // 1110 xxxx  all-Channel, -1dB/step
#define PT2258_Reg_6CH_10db_STEP       0xD0        // 1101 0xxx  all-Channel, -10dB/step
#define PT2258_Reg_CH1_1db_STEP        0x90        // 1001 xxxx  Channel No. 1, -1dB/step
#define PT2258_Reg_CH1_10db_STEP       0x80        // 1000 0xxx  Channel No. 1, -10dB/step
#define PT2258_Reg_CH2_1db_STEP        0x50        // 0101 xxxx  Channel No. 2, -1dB/step
#define PT2258_Reg_CH2_10db_STEP       0x40        // 0100 0xxx  Channel No. 2, -10dB/step
#define PT2258_Reg_CH3_1db_STEP        0x10        // 0001 xxxx  Channel No. 3, -1dB/step
#define PT2258_Reg_CH3_10db_STEP       0x00        // 0000 0xxx  Channel No. 3, -10dB/step
#define PT2258_Reg_CH4_1db_STEP        0x30        // 0011 xxxx  Channel No. 4, -1dB/step
#define PT2258_Reg_CH4_10db_STEP       0x20        // 0010 0xxx  Channel No. 4, -10dB/step
#define PT2258_Reg_CH5_1db_STEP        0x70        // 0111 xxxx  Channel No. 5, -1dB/step
#define PT2258_Reg_CH5_10db_STEP       0x60        // 0110 0xxx  Channel No. 5, -10dB/step
#define PT2258_Reg_CH6_1db_STEP        0xB0        // 1011 xxxx  Channel No. 6, -1dB/step
#define PT2258_Reg_CH6_10db_STEP       0xA0        // 1010 0xxx  Channel No. 6, -10dB/step
#define PT2258_Reg_6CH_MUTE_OFF        0xF8        // 1111 100x  all-Channel, Mute When M= 0, MUTE OFF
#define PT2258_Reg_6CH_MUTE_ON         0xF9        // 1111 100x  all-Channel, Mute When M= 1, MUTE ON

#define IIC_ADDR_PT2258				0x80			//CODE[1:2]都接GND时的iicAddr;


//用户可调节音量范围[1,100](percent)
uint8_t pt2258_volPercentMap[101]={
	0,
	1, 3, 4, 5, 6, 8, 9, 10,11,13,
	14,15,16,18,19,20,21,23,24,25,
	26,28,29,30,31,33,34,35,36,38,
	39,40,41,43,44,45,46,48,49,50,
	51,53,54,55,56,58,59,60,61,63,
	64,65,66,68,69,70,71,73,74,75,
	76,78,79,80,81,83,84,85,86,88,
	89,90,91,93,94,95,96,98,99,100,
};

//PT2258可调节音量范围[-79,0](dB)
uint8_t pt2258_dBMap[81]={
	80,
	79,78,77,76,75,74,73,72,71,70,
	69,68,67,66,65,64,63,62,61,60,
	59,58,57,56,55,54,53,52,51,50,
	49,48,47,46,45,44,43,42,41,40,
	39,38,37,36,35,34,33,32,31,30,
	29,28,27,26,25,24,23,22,21,20,
	19,18,17,16,15,14,13,12,11,10, 
	 9, 8, 7, 6, 5, 4, 3, 2, 1, 0
};



void pt2258_iic_writeByte(eIIC_BUS_ID busId,uint8_t iicAddr,uint8_t data1, uint8_t data2){

	PRT_PT2258("pt2258_iic_writeByte() ");

	eRESULT  eResult = rcSUCCESS;
	uint32_t regData = (uint32_t)((data1<<8)|data2);
	uint32_t pLen = 0;
	uint8_t *pBuff = NULL;
	uint32_t regIs2Flag = FLG_IIC_WADDR;
	
	eResult = dvDeviceBusWrite(busId,iicAddr,regData,pLen,pBuff,regIs2Flag);
	if(eResult){
		PRT_PT2258("PT2258 iic fail. ");
	}
}



void PT2258_AdjustFunction(u8 busID,u8 ch,u8 dBValue)
{
    u8 VolumeVaule_10db = 0;
    u8 VolumeVaule_1db = 0;
    switch(ch){
    case 1:
        VolumeVaule_1db = PT2258_Reg_CH1_1db_STEP|((pt2258_dBMap[dBValue]%10)&0xF);
        VolumeVaule_10db = PT2258_Reg_CH1_10db_STEP|((pt2258_dBMap[dBValue]/10)&0x7);
    	break;
    case 2:
        VolumeVaule_1db = PT2258_Reg_CH2_1db_STEP|((pt2258_dBMap[dBValue]%10)&0xF);
        VolumeVaule_10db = PT2258_Reg_CH2_10db_STEP|((pt2258_dBMap[dBValue]/10)&0x7);
    	break;
    case 3:
        VolumeVaule_1db = PT2258_Reg_CH3_1db_STEP|((pt2258_dBMap[dBValue]%10)&0xF);
        VolumeVaule_10db = PT2258_Reg_CH3_10db_STEP|((pt2258_dBMap[dBValue]/10)&0x7);
    	break;
    case 4:
        VolumeVaule_1db = PT2258_Reg_CH4_1db_STEP|((pt2258_dBMap[dBValue]%10)&0xF);
        VolumeVaule_10db = PT2258_Reg_CH4_10db_STEP|((pt2258_dBMap[dBValue]/10)&0x7);
    	break;
    case 5:
        VolumeVaule_1db = PT2258_Reg_CH5_1db_STEP|((pt2258_dBMap[dBValue]%10)&0xF);
        VolumeVaule_10db = PT2258_Reg_CH5_10db_STEP|((pt2258_dBMap[dBValue]/10)&0x7);
    	break;
    case 6:
        VolumeVaule_1db = PT2258_Reg_CH6_1db_STEP|((pt2258_dBMap[dBValue]%10)&0xF);
        VolumeVaule_10db = PT2258_Reg_CH6_10db_STEP|((pt2258_dBMap[dBValue]/10)&0x7);
    	break;
    default:
        VolumeVaule_1db = PT2258_Reg_6CH_1db_STEP|((pt2258_dBMap[dBValue]%10)&0xF);
        VolumeVaule_10db = PT2258_Reg_6CH_10db_STEP|((pt2258_dBMap[dBValue]/10)&0x7);
        break;
    }

    pt2258_iic_writeByte(busID, IIC_ADDR_PT2258, VolumeVaule_1db, VolumeVaule_10db);
}





void PT2258_VolumeAdjust(uint8_t busID, uint8_t ch, float vol){
	
	uint8_t dBPercent = (uint8_t)(vol*0.8);
	if(dBPercent<1){
		dBPercent=1;
	}

	PRT_PT2258("PT2258_VolumeAdjust()------ch:%d db:%d",ch,dBPercent);
    PT2258_AdjustFunction(busID,ch,dBPercent);
}


void PT2258_VolumeMute(uint8_t busID,uint8_t muteFlag){

	PRT_PT2258("PT2258_VolumeMute() ");
    if(muteFlag){
        pt2258_iic_writeByte(busID, IIC_ADDR_PT2258, PT2258_Reg_6CH_MUTE_ON,PT2258_Reg_6CH_MUTE_ON);
    }
    else{
        pt2258_iic_writeByte(busID, IIC_ADDR_PT2258, PT2258_Reg_6CH_MUTE_OFF,PT2258_Reg_6CH_MUTE_OFF);
    }
}

5 小结

  PT2258的软件还是比较简单的，因为软件需要调节的也不多，只需要通过iic发送3个字符就完了；

  如果调节声音就通过iic总线发送对应dB值给到PT2258；如果静音就通过iic总线发送对应静音或不静音指令给到PT2258；

  如果调节2258旋钮有pongpong声，那就看看实际电路是否和参考电路对不上，电阻电容取值位置对不对；

  如果断上电时有pongpong声，那就在断上电之前先mute了PT2258；

  参考文档：PT2257在数字音量控制系统中的应用