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MAX1233/MAX1234觸摸屏控制器入門(mén)

作者： 時(shí)間：2012-03-17 來(lái)源：網(wǎng)絡(luò) 收藏
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(duì)比時(shí)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(cè)量外部電壓輸入AUX1、AUX2、BAT1、BAT2和溫度

表9. ADC測(cè)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(lái)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(jià)格范圍在50美元至10美元之間，價(jià)格取決于型號(hào)以及玻璃是否全部貼在顯示屏上。

3.2) 連接觸摸屏和評(píng)估板

MAX1234評(píng)估板提供突出插頭H5/H6來(lái)連接10mm柔性電纜或者長(zhǎng)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(cè)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(guò)下面的步驟來(lái)驗(yàn)證X和Y連接是否正確?？梢杂袔讉€(gè)觸摸屏交叉連接，但大部分不會(huì)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(wèn)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(cè)觸摸屏的操作：根據(jù)需要掃描

在配置MAX1234檢測(cè)觸摸屏操作，根據(jù)需要數(shù)字化接觸屏的位置時(shí)，寫(xiě)入寄存器0x40 (ADC控制)，其PENSTS=0，ADSTS=0 (請(qǐng)參考MAX1233/MAX1234數(shù)據(jù)資料的表6)。讀取寄存器0x00 (X軸)后，檢測(cè)到后續(xù)的觸摸屏操作時(shí)，/PENIRQ信號(hào)鎖存至低電平，在寫(xiě)入ADC控制寄存器測(cè)量X、Y軸之前，保持低電平。

表12. 觸摸屏檢測(cè)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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