タッチスクリーン

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タッチスクリーン - (2007/06/27 (水) 22:14:01) の１つ前との変更点

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TI社の TSC2046 コントローラが入ってます。
ARM7 の SPI ポートに繋がってます。
 News at 9.

コマンドフォーマット
|bit|名前|説明|
|7|S|Start bit|
|6..4|A2..A0|Channel select|
|3|Mode	12 bit/8 bit|conversion mode|
|2|SER/DFR|read type|
|1..0|PD1..PD0|power-down mode|

Power down mode:
PD1	PD0	/PENIRQ	Description
0	0	Enabled	Power-down between conversions
0	1	Disabled	Voltage reference off, ADC on
1	0	Enabled	Voltage reference on, ADC off
1	1	Disabled	Device always powered. Voltage reference on, ADC on

/PENIRQ is wired to bit 6 of R2_CR

The DS has wired an external VREF of 3.3 V to the TSC, instead of using the internal 2.5 VREF. This impacts the temperature calculations below, and converting any reading into an actual voltage.

Useful commands:
Constant	Value	Notes
TSC_MEASURE_TEMP1	0x84	Measures temperature diode 1
TSC_MEASURE_Y	0x94	Measures Y position
TSC_MEASURE_BATTERY	0xA4	Does not work on DS, VBAT is grounded
TSC_MEASURE_Z1	0xB4	Measures cross-panel position 1
TSC_MEASURE_Z2	0xC4	Measures cross-panel position 2
TSC_MEASURE_X	0xD4	Measures X position
TSC_MEASURE_AUX	0xE4	Measures ?, its non-zero, but I don't know what
TSC_MEASURE_TEMP2	0xF4	Measures temperature diode 2

A 12-bit measurment cycle consists of 3 SPI byte transfers:

    * The first transfer sends the command and returns no meaningful data.
    * The second transfer returns 0 measurement(11)..measurment(5)
    * The third transfer returns measurment(4..0) 000 

Thus, pseudocode for measuring a TSC input is:

 
BlockingWriteSPI(command);
data = BlockingWriteSPI(0);
data = (data << 5) | (BlockingWriteSPI(0) >> 3);


Temperature calculation:

Temperature diode two has a 91 times larger current, and the absolute temperature can be calculated based on the measurements of the two sensors. I'll present a fixed point algorithm for computing the temperature in degrees C (see the TSC 2046 datasheet for the original equation).
temperature(deg C) = 8490 * (V_I91 - V_I1) - 273*4096; (in 20.12 fixed point)
Reading from the touchscreen controller (SPI)

 
uint16 touchRead(uint32 command) {
  uint16 result;
  while (SERIAL_CR & SERIAL_BUSY) swiDelay(1);

  // Write the command and wait for it to complete
  SERIAL_CR = SERIAL_ENABLE | 0x800 | 0x201;
  SERIAL_DATA = command;
  while (SERIAL_CR & SERIAL_BUSY) swiDelay(1);

  // Write the second command and clock in part of the data
  SERIAL_DATA = 0;
  while (SERIAL_CR & SERIAL_BUSY) swiDelay(1);
  result = SERIAL_DATA;

  // Clock in the rest of the data (last transfer)
  SERIAL_CR = SERIAL_ENABLE | 0x201;
  SERIAL_DATA = 0;
  while (SERIAL_CR & SERIAL_BUSY) swiDelay(1);

  // Return the result
  return ((result & 0x7F) << 5) | (SERIAL_DATA >> 3);
}


Todo: figure out what bit 11, bit 9, and bit 0 are doing (bit 0 is probably the CR select, since the firmware reads have this bit cleared)
Position calculation

 
 #define SCREEN_WIDTH   256
 #define SCREEN_HEIGHT   192
 
 // those are pixel positions of the two points you click when calibrating
 #define TOUCH_CNTRL_X1   (*(vu8*)0x027FFCDC)
 #define TOUCH_CNTRL_Y1   (*(vu8*)0x027FFCDD)
 #define TOUCH_CNTRL_X2   (*(vu8*)0x027FFCE2)
 #define TOUCH_CNTRL_Y2   (*(vu8*)0x027FFCE3)
 
 // those are the corresponding touchscreen values:
 #define TOUCH_CAL_X1   (*(vu16*)0x027FFCD8)
 #define TOUCH_CAL_Y1   (*(vu16*)0x027FFCDA)
 #define TOUCH_CAL_X2   (*(vu16*)0x027FFCDE)
 #define TOUCH_CAL_Y2   (*(vu16*)0x027FFCE0)
 
 // linear mapping can be used to go from touchscreen position to pixel position
 
 // precalculate some values
 static int16 TOUCH_WIDTH  = TOUCH_CAL_X2 - TOUCH_CAL_X1;
 static int16 TOUCH_HEIGHT = TOUCH_CAL_Y2 - TOUCH_CAL_Y1;
 static int16 CNTRL_WIDTH  = TOUCH_CNTRL_X2 - TOUCH_CNTRL_X1;
 static int16 CNTRL_HEIGHT = TOUCH_CNTRL_Y2 - TOUCH_CNTRL_Y1;
 
 
 // reading pixel position:
 int16 x = (IPC->touchX - (int16) TOUCH_CAL_X1) * CNTRL_WIDTH  / TOUCH_WIDTH  + (int16) TOUCH_CNTRL_X1;
 int16 y = (IPC->touchY - (int16) TOUCH_CAL_Y1) * CNTRL_HEIGHT / TOUCH_HEIGHT + (int16) TOUCH_CNTRL_Y1;


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TI社の TSC2046 コントローラが入ってます。
ARM7 の SPI ポートに繋がってます。
 News at 9.

コマンドフォーマット:
|bit|名前|説明|
|7|S|スタートビット|
|6..4|A2..A0|チャンネルセレクト|
|3|Mode|12 bit/8 bit コンバーションモード|
|2|SER/DFR|読み込みタイプ|
|1..0|PD1..PD0|パワーダウンモード|

パワーダウンモード:
|PD1|PD0|/PENIRQ|Description|
|0|0|Enabled|Power-down between conversions|
|0|1|Disabled|Voltage reference off, ADC on|
|1|0|Enabled|Voltage reference on, ADC off|
|1|1|Disabled|Device always powered. Voltage reference on, ADC on|

/PENIRQ は、R2_CR の bit 6 に繋がれています。

The DS has wired an external VREF of 3.3 V to the TSC, instead of using the internal 2.5 VREF. This impacts the temperature calculations below, and converting any reading into an actual voltage.

便利なコマンド:
|Constant|Value|Notes|
|TSC_MEASURE_TEMP1|0x84|Measures temperature diode 1|
|TSC_MEASURE_Y|0x94|Measures Y position|
|TSC_MEASURE_BATTERY|0xA4|Does not work on DS, VBAT is grounded|
|TSC_MEASURE_Z1|0xB4|Measures cross-panel position 1|
|TSC_MEASURE_Z2|0xC4|Measures cross-panel position 2|
|TSC_MEASURE_X|0xD4|Measures X position|
|TSC_MEASURE_AUX|0xE4|Measures ?, its non-zero, but I don't know what|
|TSC_MEASURE_TEMP2|0xF4|Measures temperature diode 2|

A 12-bit measurment cycle consists of 3 SPI byte transfers:

-The first transfer sends the command and returns no meaningful data.
-The second transfer returns 0 measurement(11)..measurment(5)
-The third transfer returns measurment(4..0) 000 

Thus, pseudocode for measuring a TSC input is:

 
 BlockingWriteSPI(command);
 data = BlockingWriteSPI(0);
 data = (data << 5) | (BlockingWriteSPI(0) >> 3);


温度計算:

Temperature diode two has a 91 times larger current, and the absolute temperature can be calculated based on the measurements of the two sensors. I'll present a fixed point algorithm for computing the temperature in degrees C (see the TSC 2046 datasheet for the original equation).
temperature(deg C) = 8490 * (V_I91 - V_I1) - 273*4096; (in 20.12 fixed point)
Reading from the touchscreen controller (SPI)

 
 uint16 touchRead(uint32 command) {
  uint16 result;
  while (SERIAL_CR & SERIAL_BUSY) swiDelay(1);
 
  // Write the command and wait for it to complete
  SERIAL_CR = SERIAL_ENABLE | 0x800 | 0x201;
  SERIAL_DATA = command;
  while (SERIAL_CR & SERIAL_BUSY) swiDelay(1);
 
  // Write the second command and clock in part of the data
  SERIAL_DATA = 0;
  while (SERIAL_CR & SERIAL_BUSY) swiDelay(1);
  result = SERIAL_DATA;
 
  // Clock in the rest of the data (last transfer)
  SERIAL_CR = SERIAL_ENABLE | 0x201;
  SERIAL_DATA = 0;
  while (SERIAL_CR & SERIAL_BUSY) swiDelay(1);
 
  // Return the result
  return ((result & 0x7F) << 5) | (SERIAL_DATA >> 3);
 }


Todo: figure out what bit 11, bit 9, and bit 0 are doing (bit 0 is probably the CR select, since the firmware reads have this bit cleared)
Position calculation

 
 #define SCREEN_WIDTH   256
 #define SCREEN_HEIGHT   192
 
 // those are pixel positions of the two points you click when calibrating
 #define TOUCH_CNTRL_X1   (*(vu8*)0x027FFCDC)
 #define TOUCH_CNTRL_Y1   (*(vu8*)0x027FFCDD)
 #define TOUCH_CNTRL_X2   (*(vu8*)0x027FFCE2)
 #define TOUCH_CNTRL_Y2   (*(vu8*)0x027FFCE3)
 
 // those are the corresponding touchscreen values:
 #define TOUCH_CAL_X1   (*(vu16*)0x027FFCD8)
 #define TOUCH_CAL_Y1   (*(vu16*)0x027FFCDA)
 #define TOUCH_CAL_X2   (*(vu16*)0x027FFCDE)
 #define TOUCH_CAL_Y2   (*(vu16*)0x027FFCE0)
 
 // linear mapping can be used to go from touchscreen position to pixel position
 
 // precalculate some values
 static int16 TOUCH_WIDTH  = TOUCH_CAL_X2 - TOUCH_CAL_X1;
 static int16 TOUCH_HEIGHT = TOUCH_CAL_Y2 - TOUCH_CAL_Y1;
 static int16 CNTRL_WIDTH  = TOUCH_CNTRL_X2 - TOUCH_CNTRL_X1;
 static int16 CNTRL_HEIGHT = TOUCH_CNTRL_Y2 - TOUCH_CNTRL_Y1;
 
 
 // reading pixel position:
 int16 x = (IPC->touchX - (int16) TOUCH_CAL_X1) * CNTRL_WIDTH  / TOUCH_WIDTH  + (int16) TOUCH_CNTRL_X1;
 int16 y = (IPC->touchY - (int16) TOUCH_CAL_Y1) * CNTRL_HEIGHT / TOUCH_HEIGHT + (int16) TOUCH_CNTRL_Y1;


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