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          EEPW首頁 
	 > 模擬技術(shù) > 設(shè)計應(yīng)用 > MAX1233/MAX1234觸摸屏控制器入門
          
    
          

          

          


	
	
	

          
	
          
		
          
			
          MAX1233/MAX1234觸摸屏控制器入門
          
						
          
				作者：
				時間：2012-03-17
				來源：網(wǎng)絡(luò)
				
				
				
				
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			1100 /* measure TEMP1,TEMP2 */
          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 0x3301
          T R T1
          Read TEMP1 result TEMP1 _code
          0x8009 0x0000
          T R T2
          Read TEMP2 result TEMP2 _code
          0x800a 0x0000

          2.8) 將TEMP1轉(zhuǎn)換結(jié)果譯為物理值
          下面的C/C++偽代碼片斷總結(jié)了DEMO1234程序是怎樣解釋TEMP1轉(zhuǎn)換結(jié)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. *//* TEMP1_code is the 16-bit result read by SPI command 0x8009 */double TEMP1_Voltage = (TEMP1_code * ADC_fullscale_voltage) / num_codes;/* Calibration values */const double Temp1V_Room = 0.590; // temp1 voltage at room temperature 25Cconst double Temp1K_Room = 298.15;  // Room temperature Kelvins (298.15K=25C)const double Temp1V_Per_K = -0.002; // TempCo -2mV per degree C/* Convert to absolute temperature */double Kelvin = (TEMP1_Voltage - Temp1V_Room) / Temp1V_Per_K + Temp1K_Room;/* Optional conversion to commonly used temperature units */double Centigrade = Kelvin - 273.15;double Fahrenheit = (Centigrade * 9.0 / 5.0) + 32;
          2.9) 將TEMP1和TEMP2轉(zhuǎn)換結(jié)果譯為物理值
          下面的C/C++偽代碼片斷總結(jié)了DEMO1234程序是怎樣解釋TEMP1和TEMP2轉(zhuǎn)換結(jié)果的。TEMP2只在和TEMP1對比時才有意義。 
              /* 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. *//* TEMP1_code is the 16-bit result read by SPI command 0x8009 */double TEMP1_Voltage = (TEMP1_code * ADC_fullscale_voltage) / num_codes;/* TEMP2_code is the 16-bit result read by SPI command 0x800a */double TEMP2_Voltage = (TEMP2_code * ADC_fullscale_voltage) / num_codes;/* Calibration values */const double K_Per_Temp21_Delta_V = 2680.0; // nominal 2680 5/27/2002/* Convert to absolute temperature */double Kelvin = (TEMP2_Voltage - TEMP1_Voltage) * K_Per_Temp21_Delta_V;/* Optional conversion to commonly used temperature units */double Centigrade = Kelvin - 273.15;double Fahrenheit = (Centigrade * 9.0 / 5.0) + 32;
          2.10) 測量外部電壓輸入AUX1、AUX2、BAT1、BAT2和溫度
          表9. ADC測量命令序列 
          DEMO1234 Command
          		Action (Triggered by A/D3210 Bits)
          SPI data in
          T MB
          		Measure BAT1/4, BAT2/4, AUX1, AUX2, TEMP1, TEMP2 with 12-bit resolution and 3.5μs conversion rate
          0x0040 0x2f01

          0x8005 0x0000

          0x8006 0x0000

          0x8007 0x0000

          0x8008 0x0000

          0x8009 0x0000

          0x800a 0x0000
          T W AC 2f01
          		Trigger ADC scan of BAT1-2, AUX1-2, TEMP1-2;
          ADC control word 0x2f01 means:
          ADC_control_wr_demand_scan
          ADC_control_ AD1011 /* measure AUX1 etc. */
          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 0x2f01
          T R B1
          		Read BAT1 result BAT1 _code
          0x8005 0x0000
          T R B2
          		Read BAT2 result BAT2_code
          0x8006 0x0000
          T R A1
          		Read AUX1 result AUX1 _code
          0x8007 0x0000
          T R A2
          		Read AUX2 result AUX2 _code
          0x8008 0x0000
          T R T1
          		Read TEMP1 result TEMP1 _code
          0x8009 0x0000
          T R T2
          		Read TEMP2 result TEMP2 _code
          0x800a 0x0000

          3) 觸摸屏實(shí)例
          下面的例子解釋了怎樣使用DEMO1234.EXE程序來獲得觸摸屏數(shù)據(jù)。

          3.1) 低成本商用觸摸屏
          在互聯(lián)網(wǎng)上搜索"PDA Digitizer/Glasstop"，尋找合適的替代觸摸屏。高清觸摸屏玻璃的價格范圍在50美元至10美元之間，價格取決于型號以及玻璃是否全部貼在顯示屏上。

          3.2) 連接觸摸屏和評估板
          MAX1234評估板提供突出插頭H5/H6來連接10mm柔性電纜或者長度更短的電纜。H6連接器的間距是0.5mm，比實(shí)際觸摸屏柔性電纜間距更精細(xì)。把柔性電纜插入H6，上鎖，選擇位于四條柔性電纜中每一電纜中心位置的H5引腳。跳接器連接H5和標(biāo)有U1的X+、Y+、X-以及Y-測試點(diǎn)。

          3.3) 檢驗(yàn)觸摸屏的連接
          第一次連接觸摸屏?xí)r，通過下面的步驟來驗(yàn)證X和Y連接是否正確?？梢杂袔讉€觸摸屏交叉連接，但大部分不會正常工作。在這些例子中，我們假設(shè)X- = left，X+ = right，Y- = top，Y+ = bottom。

          表10. 觸摸屏物理連接驗(yàn)證命令序列 
          DEMO1234 Command
          		Action
          SPI data in
          		Verification
          Connect DVM to X+/GND
          T MD
          		No measurement; drive Y+,Y-
          0x0040 0x3701
          Touch top leftX+ = approx. Y-
          Touch top rightX+ = approx. Y-
          Touch bottom leftX+ = approx. Y+
          Touch bottom rightX+ = approx. Y+
          Connect DVM to Y+/GND
          T ME
          		No measurement; drive X+,X-
          0x0040 0x3b01
          Touch top leftY+ = approx. X-
          Touch top rightY+ = approx. X+
          Touch bottom leftY+ = approx. X-
          Touch bottom rightY+ = approx. X+

          表11. 糾正觸摸屏連接問題 
          SymptomCorrection
          Touch coordinates are mirrored top-to-bottomSwap the Y+ and Y- connections
          Touch coordinates are mirrored left-to-rightSwap the X+ and X- connections
          Touch coordinates are rotated 180 degreesSwap the X+ and X- connections, and swap the Y+ and Y- connections
          Touch coordinates are mirrored diagonallySwap the X+ and Y+ connections, and swap the X- and Y- connections
          Touch coordinates do not seem to track, and the distortion is not a simple flip/rotate/mirror transformationSwap the X+ and Y+ connections;
          if distortion persists, swap the X+ and Y- connections;
          if distortion still persists, disconnect touch screen and use DVM to verify X+ to X- resistance and Y+ to Y- resistance;
          verify with no touch X+ and X- are isolated from Y+ and Y-

          3.4) 檢測觸摸屏的操作：根據(jù)需要掃描
          在配置MAX1234檢測觸摸屏操作，根據(jù)需要數(shù)字化接觸屏的位置時，寫入寄存器0x40 (ADC控制)，其PENSTS=0，ADSTS=0 (請參考MAX1233/MAX1234數(shù)據(jù)資料的表6)。讀取寄存器0x00 (X軸)后，檢測到后續(xù)的觸摸屏操作時，/PENIRQ信號鎖存至低電平，在寫入ADC控制寄存器測量X、Y軸之前，保持低電平。 

          表12. 觸摸屏檢測命令序列：根據(jù)需要掃描 
          DEMO1234 Command
          		Action
          SPI data in
          		Verification
          T W AC 0b01
          		Demand scan
          0x0040 0x0b01
          T R AX
          		Read conversion result register X
          0x8000 0x0000
          P R 
				
            
                
			
							
          
                
			            
                            
              
            
		
		
          
		
          
		
          
		
          
			
            
				
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          關(guān)鍵詞：
            			            MAX1233
                        MAX1234
                        觸摸屏
                        控制器
                        
            
          
            
			
          
		
          	
		

	

          
	
	
          
		
          
			
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