PIC18F4520: Serial Digital-to-Analog Conversion - Revision history

LIMS: /* Sample Code */

2007-07-05T15:26:06Z

Sample Code

← Older revision		Revision as of 10:26, 5 July 2007
Line 47:		Line 47:
	int read;		int read;

	Setup analog inputs. AN0 can be replaced by ALL_ANALOG, ~~AN1~~, ~~AN2~~,		Setup analog inputs. AN0 can be replaced by ALL_ANALOG, AN0_TO_AN1, AN0_TO_AN8,
	etc.		etc.

LIMS: /* Sample Code */

2007-07-05T15:25:04Z

Sample Code

← Older revision		Revision as of 10:25, 5 July 2007
Line 26:		Line 26:

	First include header file with definitions for specific PIC.		First include header file with definitions for specific PIC.
	Set fuses. HS is type of external clock, low voltage ~~protection~~		Set fuses. HS is type of external clock, low voltage programming
	(LVP) is off, and the watchdog timer (WDT) is off.		(LVP) is off, and the watchdog timer (WDT) is off.
	External clock frequency of 20 MHz is specified.		External clock frequency of 20 MHz is specified.

LIMS at 13:43, 5 July 2007

2007-07-05T13:43:09Z

← Older revision		Revision as of 08:43, 5 July 2007
Line 1:		Line 1:
	Since PIC microcontrollers do not offer analog outputs, a Digital-to-Analog converter (DAC) must be used to ~~obtain~~ an analog signal. An eight bit digital number can be converted to analog by using eight of the output pins from the PIC MCU to a separate DAC chip, however if more than one conversion is neccessary, this will quickly use up many of the available output pins from the PIC microcontroller, and require extensive wiring. Luckily, there is an easier and more effective way of doing this using <math>I^2C</math> communication. <math>I^2C</math> utilizes two lines to communicate, usually called ''SCL'' and ''SDA'' (a clock line and a data line). A "master" produces an <math>I^2C</math> signal which is sent to the "slave" to work with. Many slaves can be controlled by one master, as long as no slave addresses are used more than once (the number of possible slave addresses is limited by the specific chip being used as a slave). If the slave chip has two programmable address bits, then four slaves can be controlled by one master. If there are three address bits, then eight slaves can be controlled by one master. Communication begins with a start condition (the clock line being held high while the data line is dropped low) and ends with a stop condition (clock line held high while the data line is brought from low to high).		Since PIC microcontrollers do not offer analog outputs, a Digital-to-Analog converter (DAC) must be used to output an analog signal. An eight bit digital number can be converted to analog by using eight of the output pins from the PIC MCU to a separate DAC chip, however if more than one conversion is neccessary, this will quickly use up many of the available output pins from the PIC microcontroller, and require extensive wiring. Luckily, there is an easier and more effective way of doing this using <math>I^2C</math> communication. <math>I^2C</math> utilizes two lines to communicate, usually called ''SCL'' and ''SDA'' (a clock line and a data line). A "master" produces an <math>I^2C</math> signal which is sent to the "slave" to work with. Many slaves can be controlled by one master, as long as no slave addresses are used more than once (the number of possible slave addresses is limited by the specific chip being used as a slave). If the slave chip has two programmable address bits, then four slaves can be controlled by one master. If there are three address bits, then eight slaves can be controlled by one master. Communication begins with a start condition (the clock line being held high while the data line is dropped low) and ends with a stop condition (clock line held high while the data line is brought from low to high).
	<br><br>		<br><br>
	[[Image:startstopcond.jpg\|center]]		[[Image:startstopcond.jpg\|center]]

LIMS: /* Sample Code */

2007-07-02T16:42:18Z

Sample Code

@@ Line 23: / Line 23: @@
 This example shows how to use <math>I^2C</math> to communicate with a DAC.  The PIC MCU will take an analog input (0-5V), and through <math>I^2C</math> communication it will utilize an external DAC to display the input voltage.  Obviously this is of no practical use, but is meant as an excercise with <math>I^2C</math> and digital-to-analog conversion.
 ===Sample Code===
 ===Circuit Diagram===
 [[Image:DACckt2.jpg]]

LIMS: /* Example of $I^2C$ Communication */

2007-07-02T16:09:03Z

Example of <math>I^2C</math> Communication

← Older revision		Revision as of 11:09, 2 July 2007
Line 22:		Line 22:
	==Example of <math>I^2C</math> Communication==		==Example of <math>I^2C</math> Communication==
	This example shows how to use <math>I^2C</math> to communicate with a DAC. The PIC MCU will take an analog input (0-5V), and through <math>I^2C</math> communication it will utilize an external DAC to display the input voltage. Obviously this is of no practical use, but is meant as an excercise with <math>I^2C</math> and digital-to-analog conversion.		This example shows how to use <math>I^2C</math> to communicate with a DAC. The PIC MCU will take an analog input (0-5V), and through <math>I^2C</math> communication it will utilize an external DAC to display the input voltage. Obviously this is of no practical use, but is meant as an excercise with <math>I^2C</math> and digital-to-analog conversion.
			===Sample Code===
			===Circuit Diagram===
			[[Image:DACckt2.jpg]]

LIMS: /* Example of $I^2C$ Communication */

2007-07-02T16:07:24Z

Example of <math>I^2C</math> Communication

← Older revision		Revision as of 11:07, 2 July 2007
Line 21:		Line 21:
	Using these three functions, one can program whatever information is required to the slave device.		Using these three functions, one can program whatever information is required to the slave device.
	==Example of <math>I^2C</math> Communication==		==Example of <math>I^2C</math> Communication==
	This example shows how to use <math>I^2C</math> to communicate with a DAC. The PIC MCU will take an analog input (0-5V), and through <math>I^2C</math> communication it will utilize an external DAC to ~~dispaly~~ the input voltage. Obviously this is of no practical use, but is meant as an excercise with <math>I^2C</math> and digital-to-analog conversion.		This example shows how to use <math>I^2C</math> to communicate with a DAC. The PIC MCU will take an analog input (0-5V), and through <math>I^2C</math> communication it will utilize an external DAC to display the input voltage. Obviously this is of no practical use, but is meant as an excercise with <math>I^2C</math> and digital-to-analog conversion.

LIMS: /* Example of $I^2C$ Communication */

2007-07-02T16:07:03Z

Example of <math>I^2C</math> Communication

← Older revision		Revision as of 11:07, 2 July 2007
Line 21:		Line 21:
	Using these three functions, one can program whatever information is required to the slave device.		Using these three functions, one can program whatever information is required to the slave device.
	==Example of <math>I^2C</math> Communication==		==Example of <math>I^2C</math> Communication==
	This example shows how to use <math>I^2C</math> to communicate with a DAC. ~~Although~~ it is ~~kind~~ of ~~odd~~ to		This example shows how to use <math>I^2C</math> to communicate with a DAC. The PIC MCU will take an analog input (0-5V), and through <math>I^2C</math> communication it will utilize an external DAC to dispaly the input voltage. Obviously this is of no practical use, but is meant as an excercise with <math>I^2C</math> and digital-to-analog conversion.

LIMS at 15:07, 2 July 2007

2007-07-02T15:07:45Z

← Older revision		Revision as of 10:07, 2 July 2007
Line 20:		Line 20:
	<br>		<br>
	Using these three functions, one can program whatever information is required to the slave device.		Using these three functions, one can program whatever information is required to the slave device.
			==Example of <math>I^2C</math> Communication==
			This example shows how to use <math>I^2C</math> to communicate with a DAC. Although it is kind of odd to

LIMS at 15:04, 2 July 2007

2007-07-02T15:04:34Z

← Older revision		Revision as of 10:04, 2 July 2007
Line 1:		Line 1:
	Since PIC microcontrollers do not offer analog outputs, a Digital-to-Analog converter (DAC) must be used to obtain an analog signal. An eight bit digital number can be converted to analog by using eight of the output pins from the PIC MCU to a separate DAC chip, however if more than one conversion is neccessary, this will quickly use up many of the available output pins from the PIC microcontroller, and require extensive wiring. Luckily, there is an easier and more effective way of doing this using <math>I^2C</math> communication. <math>I^2C</math> utilizes two lines to communicate, usually called ''SCL'' and ''SDA'' (a clock line and a data line). A "master" produces an <math>I^2C</math> signal which is sent to the "slave" to work with. Many slaves can be controlled by one master, as long as no slave addresses are used more than once (the number of possible slave addresses is limited by the specific chip being used as a slave). Communication begins with a start condition (the clock line being held high while the data line is dropped low) and ends with a stop condition (clock line held high while the data line is brought from low to high).		Since PIC microcontrollers do not offer analog outputs, a Digital-to-Analog converter (DAC) must be used to obtain an analog signal. An eight bit digital number can be converted to analog by using eight of the output pins from the PIC MCU to a separate DAC chip, however if more than one conversion is neccessary, this will quickly use up many of the available output pins from the PIC microcontroller, and require extensive wiring. Luckily, there is an easier and more effective way of doing this using <math>I^2C</math> communication. <math>I^2C</math> utilizes two lines to communicate, usually called ''SCL'' and ''SDA'' (a clock line and a data line). A "master" produces an <math>I^2C</math> signal which is sent to the "slave" to work with. Many slaves can be controlled by one master, as long as no slave addresses are used more than once (the number of possible slave addresses is limited by the specific chip being used as a slave). If the slave chip has two programmable address bits, then four slaves can be controlled by one master. If there are three address bits, then eight slaves can be controlled by one master. Communication begins with a start condition (the clock line being held high while the data line is dropped low) and ends with a stop condition (clock line held high while the data line is brought from low to high).
	<br><br>		<br><br>
	[[Image:startstopcond.jpg\|center]]		[[Image:startstopcond.jpg\|center]]

LIMS: /* C Programming */

2007-07-02T15:01:17Z

C Programming

← Older revision		Revision as of 10:01, 2 July 2007
Line 6:		Line 6:
	==C Programming==		==C Programming==
	The basic building blocks of programming for <math>I^2C</math> communication are shown below.		The basic building blocks of programming for <math>I^2C</math> communication are shown below.
			<br><br>
			{\| border="1" cellspacing="2" cellpadding="3" align="center"
			\|-
			!Function!! Description
			\|-
			\|i2c_start()\|\| Sends a start condition
			\|-
			\|i2c_write()\|\| Writes a data byte to the slave
			\|-
			\|i2c_stop()\|\|Sends a stop condition
			\|-
			\|}
			<br>
			Using these three functions, one can program whatever information is required to the slave device.

PIC18F4520: Serial Digital-to-Analog Conversion - Revision history

LIMS: /* Sample Code */

LIMS: /* Sample Code */

LIMS at 13:43, 5 July 2007

LIMS: /* Sample Code */

LIMS: /* Example of I^2C Communication */

LIMS: /* Example of I^2C Communication */

LIMS: /* Example of I^2C Communication */

LIMS at 15:07, 2 July 2007

LIMS at 15:04, 2 July 2007

LIMS: /* C Programming */

LIMS: /* Example of $I^2C$ Communication */

LIMS: /* Example of $I^2C$ Communication */

LIMS: /* Example of $I^2C$ Communication */