DAC-Chua - Chua chaotic oscillator and MCP4922 DAC

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Kamil Ondrousek / Mbed 2 deprecated DAC-Chua

Chua chaotic oscillator and MCP4922 DAC

MCP4922.cpp@0:e5edc0373da0, 2011-05-07 (annotated)

Committer:: JLS
Date:: Sat May 07 19:27:14 2011 +0000
Revision:: 0:e5edc0373da0

Who changed what in which revision?

User	Revision	Line number	New contents of line
JLS	0:e5edc0373da0	1	/*
JLS	0:e5edc0373da0	2	* MCP4922 - DAC library.
JLS	0:e5edc0373da0	3	*/
JLS	0:e5edc0373da0	4
JLS	0:e5edc0373da0	5	#include "mbed.h"
JLS	0:e5edc0373da0	6	#include "MCP4922.h"
JLS	0:e5edc0373da0	7
JLS	0:e5edc0373da0	8	using namespace mbed;
JLS	0:e5edc0373da0	9
JLS	0:e5edc0373da0	10	int dac =0;
JLS	0:e5edc0373da0	11
JLS	0:e5edc0373da0	12	MCP4922::MCP4922(PinName mosi, PinName sclk, PinName cs) : _spi(mosi, NC, sclk) {
JLS	0:e5edc0373da0	13
JLS	0:e5edc0373da0	14	int i;
JLS	0:e5edc0373da0	15	_ndacs = 1;
JLS	0:e5edc0373da0	16	_ncs_array = new DigitalOut*[ _ndacs ];
JLS	0:e5edc0373da0	17	for (i=0; i<_ndacs; i++) {
JLS	0:e5edc0373da0	18	_ncs_array[i] = new DigitalOut(cs);
JLS	0:e5edc0373da0	19	}
JLS	0:e5edc0373da0	20
JLS	0:e5edc0373da0	21	// Initialise the DAC SPI interface.
JLS	0:e5edc0373da0	22	_init();
JLS	0:e5edc0373da0	23	}
JLS	0:e5edc0373da0	24
JLS	0:e5edc0373da0	25	// Destructor
JLS	0:e5edc0373da0	26	MCP4922::~MCP4922() {
JLS	0:e5edc0373da0	27
JLS	0:e5edc0373da0	28	// Before destroying the object, shut down all the chips.
JLS	0:e5edc0373da0	29	//shdn_all();
JLS	0:e5edc0373da0	30
JLS	0:e5edc0373da0	31	// Delete all the NCS DigitalOut objects and the array pointing to
JLS	0:e5edc0373da0	32	// them.
JLS	0:e5edc0373da0	33	int i;
JLS	0:e5edc0373da0	34	for (i=0; i<_ndacs; i++) {
JLS	0:e5edc0373da0	35	delete _ncs_array[i];
JLS	0:e5edc0373da0	36	}
JLS	0:e5edc0373da0	37	delete [] _ncs_array;
JLS	0:e5edc0373da0	38
JLS	0:e5edc0373da0	39	// Delete the LDAC DigitalOut object if it exists.
JLS	0:e5edc0373da0	40	if (_latched ) delete _nldac;
JLS	0:e5edc0373da0	41	}
JLS	0:e5edc0373da0	42
JLS	0:e5edc0373da0	43	// Initialise SPI interface.
JLS	0:e5edc0373da0	44	void MCP4922::_init() {
JLS	0:e5edc0373da0	45
JLS	0:e5edc0373da0	46	// Set up the SPI for 16-bit values (12-bit + 4 command bits) and mode 0.
JLS	0:e5edc0373da0	47	_spi.format(16, 0);
JLS	0:e5edc0373da0	48
JLS	0:e5edc0373da0	49	// Start with all the CS and LDAC signals high (disabled)
JLS	0:e5edc0373da0	50	int i;
JLS	0:e5edc0373da0	51	for (i=0; i<_ndacs; i++) {
JLS	0:e5edc0373da0	52	_ncs_array[i]->write(1);
JLS	0:e5edc0373da0	53	}
JLS	0:e5edc0373da0	54
JLS	0:e5edc0373da0	55	if (_latched ) _nldac->write(1);
JLS	0:e5edc0373da0	56	return;
JLS	0:e5edc0373da0	57	}
JLS	0:e5edc0373da0	58
JLS	0:e5edc0373da0	59	// Set SPI clock frequency.
JLS	0:e5edc0373da0	60	void MCP4922::frequency( int freq ) {
JLS	0:e5edc0373da0	61
JLS	0:e5edc0373da0	62	// Set the SPI interface clock frequency in Hz.
JLS	0:e5edc0373da0	63	_spi.frequency( freq );
JLS	0:e5edc0373da0	64	return;
JLS	0:e5edc0373da0	65	}
JLS	0:e5edc0373da0	66
JLS	0:e5edc0373da0	67	/*
JLS	0:e5edc0373da0	68	* Note: There is a lot of code in common between the following 4 functions.
JLS	0:e5edc0373da0	69	* The code is kept in line to keep it efficient. Could the functions have
JLS	0:e5edc0373da0	70	* been written as templates?
JLS	0:e5edc0373da0	71	*/
JLS	0:e5edc0373da0	72	// Write to DAC channel A with gain 1.
JLS	0:e5edc0373da0	73	void MCP4922::writeA(int value) {
JLS	0:e5edc0373da0	74
JLS	0:e5edc0373da0	75	// Set up the command register with the appropriate value.
JLS	0:e5edc0373da0	76	// For efficiency, the caller is assumed to have checked dac.
JLS	0:e5edc0373da0	77	int reg;
JLS	0:e5edc0373da0	78	//int dac = 0;
JLS	0:e5edc0373da0	79	reg = (value & 0x0FFF) \| MCP4922_REG_A1;
JLS	0:e5edc0373da0	80
JLS	0:e5edc0373da0	81	// Select the DAC chip, write to its command register and
JLS	0:e5edc0373da0	82	// then unselect the DAC chip.
JLS	0:e5edc0373da0	83	_ncs_array[dac]->write(0);
JLS	0:e5edc0373da0	84	_spi.write(reg);
JLS	0:e5edc0373da0	85	_ncs_array[dac]->write(1);
JLS	0:e5edc0373da0	86	return;
JLS	0:e5edc0373da0	87	}
JLS	0:e5edc0373da0	88
JLS	0:e5edc0373da0	89	// Write to DAC channel B with gain 1.
JLS	0:e5edc0373da0	90	void MCP4922::writeB(int value) {
JLS	0:e5edc0373da0	91
JLS	0:e5edc0373da0	92	// Set up the command register with the appropriate value.
JLS	0:e5edc0373da0	93	// For efficiency, the caller is assumed to have checked dac.
JLS	0:e5edc0373da0	94	int reg;
JLS	0:e5edc0373da0	95	reg = (value & 0x0FFF) \| MCP4922_REG_B1;
JLS	0:e5edc0373da0	96
JLS	0:e5edc0373da0	97	// Select the DAC chip, write to its command register and then
JLS	0:e5edc0373da0	98	// unselect the DAC chip.
JLS	0:e5edc0373da0	99	_ncs_array[dac]->write(0);
JLS	0:e5edc0373da0	100	_spi.write(reg);
JLS	0:e5edc0373da0	101	_ncs_array[dac]->write(1);
JLS	0:e5edc0373da0	102	return;
JLS	0:e5edc0373da0	103	}
JLS	0:e5edc0373da0	104
JLS	0:e5edc0373da0	105	// Write an array of values to the DACs.
JLS	0:e5edc0373da0	106	void MCP4922::write(int nchans, int values[], int gain, int latch) {
JLS	0:e5edc0373da0	107
JLS	0:e5edc0373da0	108	// nchans must be at least 1 but less than or equal to ndacs x 2.
JLS	0:e5edc0373da0	109	if (nchans < 1) nchans = 1;
JLS	0:e5edc0373da0	110	const int maxchans = _ndacs * 2;
JLS	0:e5edc0373da0	111	if (nchans > maxchans) nchans = maxchans;
JLS	0:e5edc0373da0	112
JLS	0:e5edc0373da0	113	if (latch && _latched)
JLS	0:e5edc0373da0	114	latch_disable();
JLS	0:e5edc0373da0	115
JLS	0:e5edc0373da0	116	int i;
JLS	0:e5edc0373da0	117
JLS	0:e5edc0373da0	118	for (i=0; i<nchans;) {
JLS	0:e5edc0373da0	119	dac = i/2;
JLS	0:e5edc0373da0	120	writeA(values[i]);
JLS	0:e5edc0373da0	121	i++;
JLS	0:e5edc0373da0	122	if (i < nchans) {
JLS	0:e5edc0373da0	123	writeB(values[i]);
JLS	0:e5edc0373da0	124	i++;
JLS	0:e5edc0373da0	125	} else break;
JLS	0:e5edc0373da0	126	}
JLS	0:e5edc0373da0	127
JLS	0:e5edc0373da0	128	// Automatically latch the new voltages if the latch flag is 1.
JLS	0:e5edc0373da0	129	if (latch && _latched)
JLS	0:e5edc0373da0	130	latch_enable();
JLS	0:e5edc0373da0	131	return;
JLS	0:e5edc0373da0	132	}
JLS	0:e5edc0373da0	133
JLS	0:e5edc0373da0	134	// Set latch signal to "enable".
JLS	0:e5edc0373da0	135	void MCP4922::latch_enable() {
JLS	0:e5edc0373da0	136
JLS	0:e5edc0373da0	137	// Latch all chips. There should be a delay of at least T_LS=40
JLS	0:e5edc0373da0	138	// nanoseconds between the last CS rising edge and the LDAC falling
JLS	0:e5edc0373da0	139	// edge. The software function calls seem to be sufficient to
JLS	0:e5edc0373da0	140	// introduce that delay. A delay may be inserted here if this
JLS	0:e5edc0373da0	141	// software is ported to a faster processor.
JLS	0:e5edc0373da0	142	if (_latched) _nldac->write(0);
JLS	0:e5edc0373da0	143	// The LDAC pulse width must be at least T_LD=100 nanoseconds long.
JLS	0:e5edc0373da0	144	// A delay can be inserted here if necessary, but so far this has
JLS	0:e5edc0373da0	145	// not been needed (see above).
JLS	0:e5edc0373da0	146	return;
JLS	0:e5edc0373da0	147	}
JLS	0:e5edc0373da0	148
JLS	0:e5edc0373da0	149	// Set latch signal to "disable".
JLS	0:e5edc0373da0	150	void MCP4922::latch_disable() {
JLS	0:e5edc0373da0	151
JLS	0:e5edc0373da0	152	// Disable latch for all chips.
JLS	0:e5edc0373da0	153	if (_latched) _nldac->write(1);
JLS	0:e5edc0373da0	154	return;
JLS	0:e5edc0373da0	155	}
JLS	0:e5edc0373da0	156

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Type:	Program
Mbed OS support:	Mbed 2 deprecated
Created:	07 May 2011
Imports:	83
Forks:	0
Commits:	1
Dependents:	0
Dependencies:	1
Followers:	4

MCP4922.cpp@0:e5edc0373da0, 2011-05-07 (annotated)

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