NU32v2: Analog Input - Revision history

Lynch at 11:25, 16 January 2016

2016-01-16T11:25:14Z

← Older revision		Revision as of 06:25, 16 January 2016
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	'''THIS PAGE REFERS TO A PRE-RELEASE VERSION OF THE NU32 PIC32 DEVELOPMENT BOARD. FOR INFORMATION, SAMPLE CODE, AND VIDEOS RELATED TO THE PRODUCTION VERSION (2016 AND LATER), AND TO THE CORRESPONDING BOOK "EMBEDDED COMPUTING AND MECHATRONICS WITH THE PIC32 MICROCONTROLLER," VISIT [[NU32\|THE NU32 PAGE]].'''		'''THIS PAGE REFERS TO A PRE-RELEASE VERSION OF THE NU32 PIC32 DEVELOPMENT BOARD. FOR INFORMATION, SAMPLE CODE, AND VIDEOS RELATED TO THE PRODUCTION VERSION (2016 AND LATER), AND TO THE CORRESPONDING BOOK "EMBEDDED COMPUTING AND MECHATRONICS WITH THE PIC32 MICROCONTROLLER," VISIT [[NU32\|THE NU32 PAGE]].'''


	'''* UNDER CONSTRUCTION *'''

	Our PIC32 has a single analog-to-digital converter (ADC) that, through the use of multiplexers, can be used to sample the analog voltage at up to 16 different pins (Port B). The ADC has 10-bit resolution, which means it can distinguish 2^10 = 1024 different voltage values, usually in the range 0 to 3.3 V, the voltage used to power the PIC32. This yields 3.3 V/1024 = 3 mV resolution. The ADC is typically used in conjunction with sensors that produce analog voltage values.		Our PIC32 has a single analog-to-digital converter (ADC) that, through the use of multiplexers, can be used to sample the analog voltage at up to 16 different pins (Port B). The ADC has 10-bit resolution, which means it can distinguish 2^10 = 1024 different voltage values, usually in the range 0 to 3.3 V, the voltage used to power the PIC32. This yields 3.3 V/1024 = 3 mV resolution. The ADC is typically used in conjunction with sensors that produce analog voltage values.

Lynch at 11:25, 16 January 2016

2016-01-16T11:25:01Z

← Older revision		Revision as of 06:25, 16 January 2016
Line 1:		Line 1:
			'''THIS PAGE REFERS TO A PRE-RELEASE VERSION OF THE NU32 PIC32 DEVELOPMENT BOARD. FOR INFORMATION, SAMPLE CODE, AND VIDEOS RELATED TO THE PRODUCTION VERSION (2016 AND LATER), AND TO THE CORRESPONDING BOOK "EMBEDDED COMPUTING AND MECHATRONICS WITH THE PIC32 MICROCONTROLLER," VISIT [[NU32\|THE NU32 PAGE]].'''


	'''* UNDER CONSTRUCTION *'''		'''* UNDER CONSTRUCTION *'''

Lynch: /* Overview */

2011-02-04T14:25:08Z

Overview

← Older revision		Revision as of 09:25, 4 February 2011
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	* '''Unipolar differential mode''': Any of the analog inputs (say AN5) can be compared to AN1, so you read the difference between the voltage on AN5 and AN1 (where the voltage on AN5 is larger than the voltage on AN1).		* '''Unipolar differential mode''': Any of the analog inputs (say AN5) can be compared to AN1, so you read the difference between the voltage on AN5 and AN1 (where the voltage on AN5 is larger than the voltage on AN1).
	* '''Interrupts''': An interrupt may be generated after a specified number of conversions.		* '''Interrupts''': An interrupt may be generated after a specified number of conversions.
	* '''ADC clock period''': The ADC clock period Tad can range from 2 times the PB clock period up to 512 times the PB clock period, in integer multiples of two. You may also choose Tad to be the period of the ADC internal RC clock. (This appears to be the period of the internal fast RC oscillator (FRC) divided by 2, or (1/8MHz)/2 = 62.5 ns. See Chapter 22 of the Data Sheet. But this appears to conflict with the data sheet requirement that Tad be at least 65 ns. Is it the period multiplied by 2, to give 250 ns?)		* '''ADC clock period''': The ADC clock period Tad can range from 2 times the PB clock period up to 512 times the PB clock period, in integer multiples of two. You may also choose Tad to be the period of the ADC internal RC clock. (This appears to be the period of the internal fast RC oscillator (FRC) divided by 2, or (1/8MHz)/2 = 62.5 ns. See Chapter 22 of the Data Sheet. But this appears to conflict with the data sheet requirement that Tad be at least 65 ns. Should it be the FRC period multiplied by 2, to give 250 ns?)
	<!--		<!--
	* '''Analog input scan''': You can set up the analog input to automatically scan through a sequence of input pins, storing the results in ADC1BUF.		* '''Analog input scan''': You can set up the analog input to automatically scan through a sequence of input pins, storing the results in ADC1BUF.

Lynch: /* Overview */

2011-02-04T14:24:31Z

Overview

← Older revision		Revision as of 09:24, 4 February 2011
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	* '''Unipolar differential mode''': Any of the analog inputs (say AN5) can be compared to AN1, so you read the difference between the voltage on AN5 and AN1 (where the voltage on AN5 is larger than the voltage on AN1).		* '''Unipolar differential mode''': Any of the analog inputs (say AN5) can be compared to AN1, so you read the difference between the voltage on AN5 and AN1 (where the voltage on AN5 is larger than the voltage on AN1).
	* '''Interrupts''': An interrupt may be generated after a specified number of conversions.		* '''Interrupts''': An interrupt may be generated after a specified number of conversions.
	* '''ADC clock period''': The ADC clock period can range from 2 times the PB clock period up to 512 times the PB clock period, in integer multiples of two.		* '''ADC clock period''': The ADC clock period Tad can range from 2 times the PB clock period up to 512 times the PB clock period, in integer multiples of two. You may also choose Tad to be the period of the ADC internal RC clock. (This appears to be the period of the internal fast RC oscillator (FRC) divided by 2, or (1/8MHz)/2 = 62.5 ns. See Chapter 22 of the Data Sheet. But this appears to conflict with the data sheet requirement that Tad be at least 65 ns. Is it the period multiplied by 2, to give 250 ns?)
	<!--		<!--
	* '''Analog input scan''': You can set up the analog input to automatically scan through a sequence of input pins, storing the results in ADC1BUF.		* '''Analog input scan''': You can set up the analog input to automatically scan through a sequence of input pins, storing the results in ADC1BUF.

Lynch: /* Overview */

2011-02-04T13:22:14Z

Overview

← Older revision		Revision as of 08:22, 4 February 2011
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	* '''Sampling and conversion initiation events''': Sampling can be initiated by a software command, or immediately after the previous conversion has completed (auto sample). Conversion can be initiated by (1) a software command, (2) the expiration of a specified sampling period (auto convert), (3) a period match with Timer 3, or (4) a signal change on the INT0 pin. Typically only the first two are relevant to us. If sampling and conversion are being done automatically (not through software commands), the conversion results will be placed in the ADC1BUF in successively higher addresses, before returning to the first address in ADC1BUF after a specified number of conversions.		* '''Sampling and conversion initiation events''': Sampling can be initiated by a software command, or immediately after the previous conversion has completed (auto sample). Conversion can be initiated by (1) a software command, (2) the expiration of a specified sampling period (auto convert), (3) a period match with Timer 3, or (4) a signal change on the INT0 pin. Typically only the first two are relevant to us. If sampling and conversion are being done automatically (not through software commands), the conversion results will be placed in the ADC1BUF in successively higher addresses, before returning to the first address in ADC1BUF after a specified number of conversions.
	* '''Input scan and alternating modes''': You can read in a single analog input at a time, or you can scan through a list of analog inputs using MUX A in the figure above. Another mode is to alternate between two inputs, one from MUX A (channel A) and one from MUX B (channel B).		* '''Input scan and alternating modes''': You can read in a single analog input at a time, or you can scan through a list of analog inputs using MUX A in the figure above. Another mode is to alternate between two inputs, one from MUX A (channel A) and one from MUX B (channel B).
	* '''Voltage reference''': The input range of the ADC is typically 0 to 3.3 V (the power rails of the PIC). If you are interested in voltages in a different range, say 1.0 V to 2.0 V, for example, you can set up the ADC so 0x000 corresponds to 1.0 V and 0x3FF corresponds to 2.0 V, to get better resolution in this smaller range: (2 V - 1 V)/1024 = 1 mV resolution. These reference voltage limits are VREF+ and VREF- and must be provided to the PIC externally.		* '''Voltage reference''': The input range of the ADC is typically 0 to 3.3 V (the power rails of the PIC). If you are interested in voltages in a different range, say 1.0 V to 2.0 V, for example, you can set up the ADC so 0x000 corresponds to 1.0 V and 0x3FF corresponds to 2.0 V, to get better resolution in this smaller range: (2 V - 1 V)/1024 = 1 mV resolution. These reference voltage limits are VREF+ and VREF- and must be provided to the PIC externally. (These must be limited to the range 0 to 3.3 V; see Table 31-36 of the Data Sheet.)
	* '''Unipolar differential mode''': Any of the analog inputs (say AN5) can be compared to AN1, so you read the difference between the voltage on AN5 and AN1 (where the voltage on AN5 is larger than the voltage on AN1).		* '''Unipolar differential mode''': Any of the analog inputs (say AN5) can be compared to AN1, so you read the difference between the voltage on AN5 and AN1 (where the voltage on AN5 is larger than the voltage on AN1).
	* '''Interrupts''': An interrupt may be generated after a specified number of conversions.		* '''Interrupts''': An interrupt may be generated after a specified number of conversions.

Lynch: /* Overview */

2011-02-04T01:47:23Z

Overview

← Older revision		Revision as of 20:47, 3 February 2011
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	* '''Interrupts''': An interrupt may be generated after a specified number of conversions.		* '''Interrupts''': An interrupt may be generated after a specified number of conversions.
	* '''ADC clock period''': The ADC clock period can range from 2 times the PB clock period up to 512 times the PB clock period, in integer multiples of two.		* '''ADC clock period''': The ADC clock period can range from 2 times the PB clock period up to 512 times the PB clock period, in integer multiples of two.
			<!--
	* '''Analog input scan''': You can set up the analog input to automatically scan through a sequence of input pins, storing the results in ADC1BUF.		* '''Analog input scan''': You can set up the analog input to automatically scan through a sequence of input pins, storing the results in ADC1BUF.
			-->
	* '''Dual buffer mode for reading and writing conversion results''': When an ADC conversion is complete, it is written into an output buffer ADC1BUF. After a series of one or more conversions is complete, an interrupt flag is set, indicating that the results are available for the program to read in. If the program is too slow to respond, however, the next set of conversions may begin to overwrite the previous results. To make this less likely, we can divide the 16-word ADC1BUF into two buffers, each consisting of 8 words: one in which the current conversions are being written, and one from which the program should read the previous results.		* '''Dual buffer mode for reading and writing conversion results''': When an ADC conversion is complete, it is written into an output buffer ADC1BUF. After a series of one or more conversions is complete, an interrupt flag is set, indicating that the results are available for the program to read in. If the program is too slow to respond, however, the next set of conversions may begin to overwrite the previous results. To make this less likely, we can divide the 16-word ADC1BUF into two buffers, each consisting of 8 words: one in which the current conversions are being written, and one from which the program should read the previous results.

Lynch: /* Sample Code */

2011-02-04T01:39:07Z

Sample Code

← Older revision		Revision as of 20:39, 3 February 2011
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	'''Auto-Convert One Channel with the Peripheral Library and Output to the Nokia 5110'''		'''Auto-Convert One Channel with the Peripheral Library and Output to the Nokia 5110'''

	The following code uses the peripheral function library, and code for the [[NU32v2: Nokia 5110 LCD]]		The following code uses the peripheral function library, and code for the [[NU32v2: Nokia 5110 LCD]]. This sample code reads the analog voltage on AN0 (Port B, pin 0) and displays it to the Nokia LCD screen.

	[[Media:NU32v2_analog_Nokia_example.zip \| Full code]] is downloadable here.		[[Media:NU32v2_analog_Nokia_example.zip \| Full code]] is downloadable here.

Lynch: /* Sample Code */

2011-02-03T21:14:33Z

Sample Code

← Older revision		Revision as of 16:14, 3 February 2011
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	while (1) {		while (1) {
	AD1CON1SET = 0x0002; // set SAMP bit. clears the DONE bit, starts sampling		AD1CON1SET = 0x0002; // set SAMP bit. clears the DONE bit, starts sampling
	for (i=0; i<10; i++); // give it enough time to settle		for (i=0; i<10; i++); // give it enough time to settle, 200 ns or more
	// a real timing operation would be better! this would fail if optimized!		// a real timing operation would be better! this would fail if optimized!
	AD1CON1CLR = 0x0002; // conversion starts when SAMP bit is cleared		AD1CON1CLR = 0x0002; // conversion starts when SAMP bit is cleared

Lynch: /* Sample Code */

2011-02-03T18:09:06Z

Sample Code

← Older revision		Revision as of 13:09, 3 February 2011
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	[[Media:NU32v2_analog_Nokia_example.zip \| Full code]] is downloadable here.		[[Media:NU32v2_analog_Nokia_example.zip \| Full code]] is downloadable here.

	~~Exerts~~ from the code:		Excerpts from the code:
	To initialize the ADC module:		To initialize the ADC module:
	<pre>		<pre>

Lynch at 18:06, 3 February 2011

2011-02-03T18:06:28Z

← Older revision		Revision as of 13:06, 3 February 2011
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	* AD1PCFG: Only the least significant 16 bits are relevant. If a bit is 0, the associated pin is configured as an analog input. If a bit is 1, it is digital I/O.		* AD1PCFG: Only the least significant 16 bits are relevant. If a bit is 0, the associated pin is configured as an analog input. If a bit is 1, it is digital I/O.
	* AD1CON1: Determines whether ADC is on or off; the output format of the conversion; the "start conversion" signal generator; whether the ADC continually does conversions or just does one sequence of samples; and whether sampling begins upon again immediately after the previous conversion ends, or waits for a signal from the user. Also indicates if the most recent conversion is finished.		* AD1CON1: Determines whether ADC is on or off; the output format of the conversion; the "start conversion" signal generator; whether the ADC continually does conversions or just does one sequence of samples; and whether sampling begins upon again immediately after the previous conversion ends, or waits for a signal from the user. Also indicates if the most recent conversion is finished.
	* AD1CON2: Determines the voltage references for the ADC (positive reference could be 3.3 V ~~and~~ VREF+, negative reference could be GND or VREF-); whether or not inputs will be scanned; whether MUX A and MUX B will be used in alternating mode; whether dual buffer mode is selected; and the number of conversions to be done before generating an interrupt.		* AD1CON2: Determines the voltage references for the ADC (positive reference could be 3.3 V or VREF+, negative reference could be GND or VREF-); whether or not inputs will be scanned; whether MUX A and MUX B will be used in alternating mode; whether dual buffer mode is selected; and the number of conversions to be done before generating an interrupt.
	* AD1CON3: Determines whether Tad is generated from the ADC internal RC clock or the PB clock; the number of Tad cycles to sample the signal; and the number of Tad cycles allowed for conversion of each bit (must be at least 65 ns).		* AD1CON3: Determines whether Tad is generated from the ADC internal RC clock or the PB clock; the number of Tad cycles to sample the signal; and the number of Tad cycles allowed for conversion of each bit (must be at least 65 ns).
	* AD1CHS: This SFR determines which pins will be sampled (the "positive" inputs) and what they will be compared to (i.e., VREF- or analog input 1). When in scan mode, the sample pins specified in this SFR are ignored.		* AD1CHS: This SFR determines which pins will be sampled (the "positive" inputs) and what they will be compared to (i.e., VREF- or analog input 1). When in scan mode, the sample pins specified in this SFR are ignored.