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MAX1233/MAX1234觸摸屏控制器入門

作者： 時間：2012-03-17 來源：網絡 收藏
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DEMO1234 Command
Action
SPI data in
MAX1233 (3.3V)MAX1234 (5.0V)
T W DD FF
DACOUT = full-scale
0x000b 0x00ff
DACOUT = 2.96VDACOUT = 4.48V
T W DD 00
DACOUT = 0V
0x000b 0x0000
DACOUT = 0.0VDACOUT = 0.0V
T W DD 80
DACOUT = mid-scale
0x000b 0x0080
DACOUT = 1.485VDACOUT = 2.25V
T W DC 8000
Disable DAC
0x0042 0x8000
DACOUT = 0.0VDACOUT = 0.0V
T W DC 0
Enable DAC
0x0042 0x0000
DACOUT = 1.485VDACOUT = 2.25V

2.2) 選擇ADC基準電源模式

ADC需要一個基準電壓。對于典型的嵌入式系統(tǒng)工作，默認設置是fine。在自動上電模式(ADC3210 = 0000，RES10 = 00)下，MAX1233/MAX1234提供自己的內部基準電壓。在每次測量之前，內部基準自動上電，測量完成后關斷。

對于第一次診斷，保持上電模式(ADC3210 = 0000，RES10 = 01)支持使用手持式DVM對基準電壓進行外部驗證。

ADC掃描選擇位設置為0000，寫入ADC控制寄存器(0x40)，來設置ADC基準電源模式。RES1/RES0位選擇基準電源模式，基準控制位RFV選擇內部1.0V或者2.5V基準(請參考MAX1233/MAX1234數(shù)據(jù)資料的表13)。

ADC控制字：x x 0 0 0 0 RES1 RES0 x x x x x x x RFV

表4. 內部基準命令 
DEMO1234 Command
Action
SPI data in
Verification
T W AC 0100
Internal 1V reference always powered; write ADC control word with
ADC3210 = 0000,
RES10 = 01,
RFV = 0
0x0040 0x0100
Voltage at pin 12 REF is between 0.98V and 1.02V
T W AC 0101
Internal 2.5V reference always powered; write ADC control word with
ADC3210 = 0000,
RES10 = 01,
RFV = 1
0x0040 0x0101
Voltage at pin 12 REF is between 2.47V and 2.53V
T W AC 0001
Internal 2.5V reference powered when needed; write ADC control word with
ADC3210 = 0000,
RES10 = 00,
RFV = 1
0x0040 0x0001
Voltage at pin 12 REF will be powered only briefly as necessary

表5. 外部基準命令 
DEMO1234 Command
Action
SPI data in
T W AC 0300
External reference must be provided;
ADC_control_wr_demand_scan:(write)demand scan
ADC_control_AD0000:configure reference
ADC_control_RES11:external reference
0x0040 0x0300

2.3) 測量外部電壓輸入AUX1和AUX2

表6. ADC測量命令序列 
DEMO1234 Command
Action (Triggered by A/D3210 Bits)
SPI data in
T M8
Measure AUX1 with 12-bit resolution and 3.5μs conversion rate
0x0040 0x2301

0x8007 0x0000
T W AC 2301
Trigger ADC scan of AUX1;
ADC control word 0x2301 means:
ADC_control_wr_demand_scan
ADC_control_AD1000 /* measure AUX1 */
ADC_control_RES11 /* 12-bit resolution */
ADC_control_AVG00 /* no averaging */
ADC_control_CNR00 /* conversion rate 3.5μs */
ADC_control_RFV /* RFV=1: VREF=2.5V */
0x0040 0x2301
T R A1
Read AUX1 result AUX1_code
0x8007 0x0000
T M9
Measure AUX2 with 12-bit resolution and 3.5μs conversion rate
0x0040 0x2701

0x8008 0x0000

2.4) 將AUX1和AUX2轉換結果譯為物理值

下面的C/C++偽代碼片斷總結了DEMO1234程序是怎樣解釋AUX1和AUX2轉換結果的。
    /* ADC control resolution value selects num_codes 4096 (12-bit), 1024 (10-bit), or 256 (8-bit) */int num_codes = 4096; /* ADC_control_RES11: 12-bit resolution *//* Voltage that corresponds to the full-scale ADC code; may be internal 1V or 2.5V ref, or ext ref. */double ADC_fullscale_voltage = 2.5; /* ADC_control_RFV=1: VREF=2.5V.  RFV=0: VREF=1.0V. *//* AUX1_code is the 16-bit result read by SPI command 0x8007 */double AUX1_Voltage = (AUX1_code * ADC_fullscale_voltage) / num_codes;/* AUX2_code is the 16-bit result read by SPI command 0x8008 */double AUX2_Voltage = (AUX2_code * ADC_fullscale_voltage) / num_codes;

2.5) 測量外部電壓輸入BAT1和BAT2

表7. ADC測量命令序列 
DEMO1234 Command
Action (Triggered by A/D3210 Bits)
SPI data in
T M6
Measure BAT1 with 12-bit resolution and 3.5μs conversion rate
0x0040 0x1b01

0x8005 0x0000
T W AC 1b01
Trigger ADC scan of BAT1;
ADC control word 0x1b01 means:
ADC_control_wr_demand_scan
ADC_control_AD0110 /* measure BAT1 */
ADC_control_RES11 /* 12-bit resolution */
ADC_control_AVG00 /* no averaging */
ADC_control_CNR00 /* conversion rate 3.5μs */
ADC_control_RFV /* RFV=1: VREF=2.5V */
0x0040 0x1b01
T R B1
Read BAT1 result BAT1_code
0x8005 0x0000
T W AC 1b21
Trigger ADC scan of BAT1;
ADC control word 0x1b21 means:
ADC_control_wr_demand_scan
ADC_control_AD0110 /* measure BAT1 */
ADC_control_RES11 /* 12-bit resolution */
ADC_control_AVG00 /* no averaging */
ADC_control_CNR10 /* conversion rate 10μs */
ADC_control_RFV /* RFV=1: VREF=2.5V */
0x0040 0x1b21
T R B1
Read BAT1 result BAT1_code
0x8005 0x0000
T M7
Measure BAT2 with 12-bit resolution and 3.5μs conversion rate
0x0040 0x1f01

0x8006 0x0000

2.6) 將BAT1和BAT2轉換結果譯為物理值

下面的C/C++偽代碼片斷總結了DEMO1234程序是怎樣解釋BAT1和BAT2轉換結果的。注意：通過一個4:1輸入分配器來測量BAT1和BAT2。 
    /* ADC control resolution value selects num_codes 4096 (12-bit), 1024 (10-bit), or 256 (8-bit) */int num_codes = 4096; /* ADC_control_RES11: 12-bit resolution *//* Voltage that corresponds to the full-scale ADC code; may be internal 1V or 2.5V ref, or ext ref. */double ADC_fullscale_voltage = 2.5; /* ADC_control_RFV=1: VREF=2.5V.  RFV=0: VREF=1.0V. *//* Note: BAT1 and BAT2 measure through a 4:1 input divider. *//* BAT1_code is the 16-bit result read by SPI command 0x8005 */double BAT1_Voltage = 4 * (BAT1_code * ADC_fullscale_voltage) / num_codes;/* BAT2_code is the 16-bit result read by SPI command 0x8006 */double BAT2_Voltage = 4 * (BAT2_code * ADC_fullscale_voltage) / num_codes;

2.7) 測量內部溫度TEMP1和TEMP2

表8. ADC測量命令序列 
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      1. DEMO1234 Command
        		Action (Triggered by A/D3210 Bits)
        SPI data in
        T MA
        		Measure TEMP1 with 12-bit resolution and 3.5μs conversion rate
        0x0040 0x2b01

        0x8009 0x0000
        T W AC 2b01
        		Trigger ADC scan of TEMP1;
        ADC control word 0x2b01 means:
        ADC_control_wr_demand_scan
        ADC_control_ AD1010 /* measure TEMP1 */
        ADC_control_RES11 /* 12-bit resolution */
        ADC_control_AVG00 /* no averaging */
        ADC_control_CNR00 /* conversion rate 3.5μs */
        ADC_control_RFV /* RFV=1: VREF=2.5V */
        0x0040 0x2b01
        T R T1
        		Read TEMP1 result TEMP1 _code
        0x8009 0x0000
        T MC
        		Measure TEMP1, TEMP2 with 12-bit resolution and 3.5μs conversion rate
        0x0040 0x3301

        0x8009 0x0000

        0x800a 0x0000
        T W AC 3301
        		Trigger ADC scan of TEMP1 and TEMP2;
        ADC control word 0x3301 means:
        ADC_control_wr_demand_scan
        ADC_control_ AD 
				
            
                
			
							
        
                
			            
                            
              
            
		
		
        
		
        
		
        
		
        
			
          
				
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