dac.c File Reference

dac function source, see simpletools.h for documentation. More...

#include "simpletools.h"

Include dependency graph for dac.c:

Go to the source code of this file.

Macros
#define	DUTY_SE   (0b110 << 26)

Functions
void	dac_ctr_cog (void *par)
void	dac_ctr_res (int bits)
	Set D/A voltage resolution. More...
void	dac_ctr (int pin, int channel, int dacVal)
	Set D/A voltage. More...
void	dac_ctr_stop (void)
	Stop the cog that's transmitting the DAC signal(s). More...

Variables
static unsigned int	stack [44+16]
static int	dacCtrBits
static unsigned int	cog
static volatile int	ctra
static volatile int	ctrb
static volatile int	frqa
static volatile int	frqb

Detailed Description

dac function source, see simpletools.h for documentation.

Author

Andy Lindsay

Version

0.86

Copyright

Copyright (C) Parallax, Inc. 2012. See end of file for terms of use (MIT License).

@detail Please submit bug reports, suggestions, and improvements to this code to edito.nosp@m.r@pa.nosp@m.ralla.nosp@m.x.co.nosp@m.m.

Definition in file dac.c.

Function Documentation

dac_ctr()

void dac_ctr	(	int	pin,
		int	channel,
		int	dacVal
	)

Set D/A voltage.

Launches process into another cog for up to two channels of D/A conversion on any I/O pin. Other libraries may be available that provide D/A for more channels. Check SimpleIDE/Learn/Simple Libraries/Convert for options. For more options, check obex.parallax.com.

This library uses another cog's counter modules (2 per cog) to perform duty modulation, which is useful for D/A conversion. The digital signal it generates will affect LED brightness. The signal can be passed through a low pass RC filter for digital to analog voltage conversion. Add an op amp buffer if it needs to drive a load.

Default resolution is 8 bits for output voltages ranging from 0 V to (255/256) of 3.3 V.

General equation is dacVal * (3.3 V/2^bits)

Default is 8 bits, which results in dacVal * (3.3 V/ 256), so dacVal specifies the number of 256ths of 3.3 V. You can change the resolution with the dac_ctr_res function.

Parameters

pin	I/O pin number.
channel	Use 0 or 1 to select the cog's CTRA or CTRB counter modules, which are used for D/A conversion.
dacVal	Number of 256ths of 3.3 V by default. Use a value from 0 (0 V) to 255 .

Definition at line 36 of file dac.c.

dac_ctr_res()

void dac_ctr_res

(

int

bits

)

Set D/A voltage resolution.

Default resolution is 8-bits for output voltages ranging from 0 V to (255/256) of 3.3 V.

General equation is dacVal * (3.3 V/2^bits)

Default is 8 bits, which results in dacVal * (3.3 V/ 256), so dacVal specifies the number of 256ths of 3.3 V.

Parameters

bits	The D/A converter's resolution in bits.

Definition at line 31 of file dac.c.

dac_ctr_stop()

void dac_ctr_stop

(

void

)

Stop the cog that's transmitting the DAC signal(s).

Stops any signals, lets go of any I/O pins, and reclaims the cog for other uses.

Definition at line 96 of file dac.c.