Interfacing with a Photodiode Array - Revision history

ErikChubb at 01:33, 11 June 2009

2009-06-11T01:33:37Z

ErikChubb at 01:26, 11 June 2009

2009-06-11T01:26:14Z

ErikChubb at 20:51, 10 June 2009

2009-06-10T20:51:20Z

ErikChubb at 20:44, 10 June 2009

2009-06-10T20:44:05Z

ErikChubb at 20:40, 10 June 2009

2009-06-10T20:40:48Z

ErikChubb at 20:37, 10 June 2009

2009-06-10T20:37:35Z

Lynch at 19:43, 10 January 2009

2009-01-10T19:43:01Z

LIMS at 18:48, 2 July 2008

2008-07-02T18:48:35Z

LIMS at 18:48, 2 July 2008

2008-07-02T18:48:18Z

LIMS at 18:48, 2 July 2008

2008-07-02T18:48:07Z

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 The TAOS Photodiode Linear Sensor Array (TSL1406R) is an array of 768 photodiodes spread over the length of about 2 inches.  Each of the individual photodiodes outputs an analog voltage which is proportional the intensity and duration of incident light.
-This duration that the photodiode is allowed to create charge is called the "integration time".  During the integration time, an dedicated capacitor (included in the TSL1406R) is charged by each of the photodiodes.  When the HOLD signal goes high, each of the charges accumulated during the integration time is simultaneously passed to its dedicated holding capacitor.  The analog voltages on each holding capacitor can then be read one-by-one at the clock speed.  Here I use the PWM function of the PIC to act as the CLK signal.
+During the "integration time", a capacitor accompanying each of the photodiodes is charged by its corresponding photodiode.  When the HOLD signal goes high, each of the charges accumulated during the integration time is simultaneously passed to a dedicated holding capacitor.  The analog voltages on each holding capacitor can then be read one-by-one at the clock speed.  Here I use the PWM function of the PIC to act as the CLK signal.
 In this particular code, the data is clocked out so quickly that it is impossible to read every analog level (since the PIC is only capable of an analog read every ~5us).  To remedy this, we low pass filter the analog output and read in analog data as quickly as possible.

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 [[Image:Expected Output.png|thumb|right|300px|Wiring Diagram]]
-The TAOS Photodiode Linear Sensor Array (TSL1406R) is an array of 768 photodiodes spread over the length of about 2 inches.  Each of the individual photodiodes outputs an analog voltage which is proportional the intensity and duration of incident light.  This duration is called the "integration time".
+The TAOS Photodiode Linear Sensor Array (TSL1406R) is an array of 768 photodiodes spread over the length of about 2 inches.  Each of the individual photodiodes outputs an analog voltage which is proportional the intensity and duration of incident light.
-During the integration time, an dedicated capacitor (included in the TSL1406R) is charged by each of the photodiodes.  When the HOLD signal goes high, each of the charges accumulated during the integration time is simultaneously passed to its dedicated holding capacitor.  The analog voltages on each holding capacitor can then be read one-by-one at the clock speed.  Here I use the PWM function of the PIC to act as the CLK signal.
+This duration that the photodiode is allowed to create charge is called the "integration time".  During the integration time, an dedicated capacitor (included in the TSL1406R) is charged by each of the photodiodes.  When the HOLD signal goes high, each of the charges accumulated during the integration time is simultaneously passed to its dedicated holding capacitor.  The analog voltages on each holding capacitor can then be read one-by-one at the clock speed.  Here I use the PWM function of the PIC to act as the CLK signal.
 In this particular code, the data is clocked out so quickly that it is impossible to read every analog level (since the PIC is only capable of an analog read every ~5us).  To remedy this, we low pass filter the analog output and read in analog data as quickly as possible.

@@ Line 8: / Line 8: @@
 In this particular code, the data is clocked out so quickly that it is impossible to read every analog level (since the PIC is only capable of an analog read every ~5us).  To remedy this, we low pass filter the analog output and read in analog data as quickly as possible.
-Each TSL1406R has two 384 photodiode arrays which can be interfaced in serial or in parallel.  This code interfaces with a single 384 pixel array.
+Each TSL1406R has two 384-pixel arrays which can be interfaced in serial or in parallel.  This code interfaces with a single 384-pixel array.
 <b>Sample code: Photodiode_array.c</b>
 [http://peshkin.mech.northwestern.edu/pic/code Link to all sample code here.]
+For code that interfaces both 384-pixel arrays, and determines a finger's position, see [[Finger Position Sensing with a Photodiode Array]]

@@ Line 8: / Line 8: @@
 In this particular code, the data is clocked out so quickly that it is impossible to read every analog level (since the PIC is only capable of an analog read every ~5us).  To remedy this, we low pass filter the analog output and read in analog data as quickly as possible.
+Each TSL1406R has two 384 photodiode arrays which can be interfaced in serial or in parallel.  This code interfaces with a single 384 pixel array.
 <b>Sample code: Photodiode_array.c</b>

@@ Line 4: / Line 4: @@
 The TAOS Photodiode Linear Sensor Array (TSL1406R) is an array of 768 photodiodes spread over the length of about 2 inches.  Each of the individual photodiodes outputs an analog voltage which is proportional the intensity and duration of incident light.  This duration is called the "integration time".
-During the integration time, a separate dedicated capacitor is charged by each of the photodiodes.  When the HOLD signal goes high, each of the charges accumulated during the integration time is simultaneously passed to its dedicated holding capacitor.  The analog voltages on each holding capacitor can then be read one-by-one at the clock speed.  Here I use the PWM function of the PIC to act as the CLK signal.
+During the integration time, an dedicated capacitor (included in the TSL1406R) is charged by each of the photodiodes.  When the HOLD signal goes high, each of the charges accumulated during the integration time is simultaneously passed to its dedicated holding capacitor.  The analog voltages on each holding capacitor can then be read one-by-one at the clock speed.  Here I use the PWM function of the PIC to act as the CLK signal.
 In this particular code, the data is clocked out so quickly that it is impossible to read every analog level (since the PIC is only capable of an analog read every ~5us).  To remedy this, we low pass filter the analog output and read in analog data as quickly as possible.

← Older revision		Revision as of 19:43, 10 January 2009
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	<b>Sample code: ~~Potodiode_array~~.c</b>		<b>Sample code: Photodiode_array.c</b>

	[http://peshkin.mech.northwestern.edu/pic/code Link to all sample code here.]		[http://peshkin.mech.northwestern.edu/pic/code Link to all sample code here.]

← Older revision		Revision as of 18:48, 2 July 2008
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	In this interfacing structure, the data is clocked out so quickly that it is impossible to read every analog level. To remedy this, we lightly low pass filter the analog output and read in analog data as quickly as possible.		In this interfacing structure, the data is clocked out so quickly that it is impossible to read every analog level. To remedy this, we lightly low pass filter the analog output and read in analog data as quickly as possible.


	<b>Sample code: Potodiode_array.c</b>		<b>Sample code: Potodiode_array.c</b>

@@ Line 6: / Line 6: @@
 In this interfacing structure, the data is clocked out so quickly that it is impossible to read every analog level.  To remedy this, we lightly low pass filter the analog output and read in analog data as quickly as possible.
-<b>Sample code</b>
+<b>Sample code: Potodiode_array.c</b>
 [http://peshkin.mech.northwestern.edu/pic/code Link to all sample code here.]