This file provides convenience functions for digital to analog conversion using using counter modules (each cog has two).

Currently supports LMM and CMM memory models. More...

#include "simpletools.h"

Data Structures
struct	DacControl
struct	DacAddr
struct	DacCogMemory

Macros
#define	DUTY_SE (6 << 26)
#define	NEW_COG 2

Typedefs
typedef struct DacControl	dac
typedef struct DacAddr	daca
typedef struct DacCogMemory	dacmem

Functions
dac	dac_setup (int pin, int channel, int bits)
	Configure an I/O pin to set a voltage with digital to analog (D/A) conversion.
void	dac_set (dac *da, int value)
	Set the D/A converter's output.
void	dac_close (dac *da)
	Clear a D/A converter that's running in the same cog and reclaim the I/O pin and counter module for other uses.
int	dac_start (dacmem mem, int sampleRate, dac da0, dac da1)
	Start D/A converter in new cog that sets voltages on either one or two pins.
int	dac_stop (int cogid)
	Stops a dac cog and frees up a cog and all its resources for other uses.

Detailed Description

This file provides convenience functions for digital to analog conversion using using counter modules (each cog has two).

Currently supports LMM and CMM memory models.

Author: Andy Lindsay

Version: 0.85

Copyright: Copyright (C) Parallax, Inc. 2013. All Rights MIT Licensed.

The current cog's counters can be used for D/A conversion, or one or more new cogs can be launched, each with two D/A channels. The output of this type of D/A converter can go straight to an LED circuit for variable brightness, or to a filter and into an op amp to drive other circuits at certain voltages. See Propeller Activity Board schematic for an example. P26 and P27 are connected to a filter, op amp, and also to LEDs.

Example in same cog:

dac myDac = dac_setup(3, 0, 8); // P3, channel 0, 8-bits (256ths of 3.3 V)
dac_set(&myDac, 128);           // Voltage to 128/256ths of 3.3 V = 1.65 V
// Call dac_set whenever you want to change the voltage

Core Usage: A call to either dac_start will launch 1 additional core that repeatedly updates DAC outputs.

Example in another cog:

// P4, channel 0, 10-bits (1024ths of 3.3 V).
dac cogDac = dac_setup(4, NEW_COG, 10);
// Optionally, pre-set the voltage (to 256/1024ths of 3.3 V = 0.825 V).
dac_set(&cogDac, 256);
// Set aside memory for the processor.
dacmem mem;
// Launch the process (we are using just one of the two available channels here).
// In another cog, you have to specify the sampling rate.  We are using 44100.
int myCog = dac_start(mem, 44100, &cogDac, NULL);

Help Improve this Library: 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.

Function Documentation

void dac_close ( dac * da )

Clear a D/A converter that's running in the same cog and reclaim the I/O pin and counter module for other uses.

Parameters

dac	Structure corresponding to the I/O pin that's sending the dac signal you want to close.

void dac_set	(	dac *	da,
		int	value
	)

Set the D/A converter's output.

After a call to dac_setup, you can use the dac structure it returns to set the D/A converter's voltage. Again, see examples at the top of this file.

Parameters

da	The pointer to the dac structure that dac_setup function returned.
value	The output value for the D/A converter. (Like the number of 256ths of 3.3 V if you set up an 8-bit D/A converter with dac_setup.

dac dac_setup	(	int	pin,
		int	channel,
		int	bits
	)

Configure an I/O pin to set a voltage with digital to analog (D/A) conversion.

Sets up a dac structure for you. You can then pass the address of this dac structure to other functions (like dac_set and/or dac_start) do things like set voltages or launch other cogs to perform D/A conversion. The technique this library uses is called duty modulation, and each D/A channel uses one of a cog's two counter modules. If you need to launch more than one D/A channel, you can use the dac structure this function returns in a call to dac_start to launch the D/A process into another cog.

Parameters

pin	Number of the I/O pin to perform D/A conversion.
channel	Use 0 for the cog's CTRA or 1 for the cog's CTRB counter module. You can also use NEW_COG if you are going to use dac_start.
bits	The resolution of your D/A converter in bits. If you set it to 8, you will be able to set voltages in terms of 256ths of 3.3 V, from 0 to 255. If you set it to 10, you will be able to set voltages in terms of the number of 1024ths of 3.3 V. More generally, the fraction of 3.3 V is 2^bits.

Returns: dac structure that you can pass by address to other functions for updating the output or launching into another cog. See examples at top of this file.

int dac_start	(	dacmem	mem,
		int	sampleRate,
		dac *	da0,
		dac *	da1
	)

Start D/A converter in new cog that sets voltages on either one or two pins.

Launches up to two D/A converters in a new cog. Example included near the top of this file.

Parameters

mem	A dacmem structure that you initialize with dacmem myStructureName;
sampleRate	The sample rate you want the dac to update values at. Top speed is 46 kHz, 44.1 kHz is recommended.
da0	Address of the dac structure the cog's channel 0 will run. If you do not want to use this channel, pass NULL.
da1	Address of the dac structure the cog's channel 1 will run. If you do not want to use this channel, pass NULL.

Returns: dac cog ID, the number of the cog the process was launched into. You can save this in case you want to use dac_stop to shut down the cog later.

int dac_stop ( int cogid )

Stops a dac cog and frees up a cog and all its resources for other uses.

Parameters

cogid The dac cog's ID that dac_start returned.

Data Structures

Macros

Typedefs

Functions

Detailed Description

Function Documentation