MAX1233/MAX1234触摸屏控制器入门

文章摘要：对于AVDD = 5.0V ±5%，DACOUT满量程范围在4.02V和4.97V之间，通常为4.48V。表3. DAC输出命令 DEMO1234 CommandActionSPI data inMAX1233 (3.3V)MAX1234 (5.0V)T W DD FFDACOUT = full-scale0x000b 0x00ffDACOUT = 2.96VDACOUT = 4.48VT W DD 00DACOUT = 0V0x000b 0x0000DACOUT = 0.0VDACOUT = 0.0VT W DD 80DACOUT = mid-scale0x000b 0x0080DACOUT

MAX1233/MAX1234触摸屏控制器入门,标签：计算机控制技术,工厂电气控制技术,http://www.88dzw.com
对于AVDD = 5.0V ±5%，DACOUT满量程范围在4.02V和4.97V之间，通常为4.48V。

表3. DAC输出命令

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

2.2) 选择ADC基准电源模式

ADC需要一个基准电压。对于典型的嵌入式系统工作，默认设置是fine。在自动上电模式(ADC3210 = 0000，RES10 = 00)下，MAX1233/MAX1234提供自己的内部基准电压。在每次测量之前，内部基准自动上电，测量完成后关断。

对于第一次诊断，保持上电模式(ADC3210 = 0000，RES10 = 01)支持使用手持式DVM对基准电压进行外部验证。

ADC扫描选择位设置为0000，写入ADC控制寄存器(0x40)，来设置ADC基准电源模式。RES1/RES0位选择基准电源模式，基准控制位RFV选择内部1.0V或者2.5V基准(请参考MAX1233/MAX1234数据资料的表13)。

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

表4. 内部基准命令

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. 外部基准命令

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) 测量外部电压输入AUX1和AUX2

表6. ADC测量命令序列

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

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