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honeywell_spi.c
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honeywell_spi.c
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/***********************************************************************
* This header file contains the honeywell_spi class definition.
* Its main purpose is to communicate with a Honeywell HSC pressure sensor with an SPI interface
* No calculations or adjustments are done and the output provided is the pure digital data coming
* the sensor's onboard analog to digital converter.
* The class contains four variables:
* mode -> defines the SPI mode used. In our case it is SPI_MODE_0.
* bitsPerWord -> defines the bit width of the data transmitted.
* This is normally 8. Experimentation with other values
* didn't work for me
* speed -> Bus speed or SPI clock frequency. According to
* https://projects.drogon.net/understanding-spi-on-the-raspberry-pi/
* It can be only 0.5, 1, 2, 4, 8, 16, 32 MHz.
* Will use 1MHz for now and test it further.
* spifd -> file descriptor for the SPI device
* ****************************************************************************/
#include "m_pd.h"
#include <unistd.h>
#include <stdint.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <linux/spi/spidev.h>
#include <stdio.h>
#include <errno.h>
#include <stdlib.h>
#include <string.h>
static t_class *honeywell_spi_class;
typedef struct _honeywell_spi
{
t_object x_obj;
t_outlet *x_out1; // honeywell pressure
t_outlet *x_out2; // honeywell temperature
t_outlet *x_out3; // honeywell status
t_outlet *x_out4; // spi status
t_symbol *spidev;
unsigned char mode;
unsigned char bitsPerWord;
unsigned int speed;
int spifd;
} t_honeywell_spi;
static t_honeywell_spi *honeywell_spi_new(t_symbol *devspi);
static int honeywell_spi_write_read(t_honeywell_spi *spi, unsigned char *data, int length);
static void honeywell_spi_open(t_honeywell_spi *spi, t_symbol *devspi);
static int honeywell_spi_close(t_honeywell_spi *spi);
static void honeywell_spi_free(t_honeywell_spi *spi);
/**********************************************************
* honeywell_spi_open() :function is called by the "open" command
* It is responsible for opening the spidev device
* "devspi" and then setting up the spidev interface.
* member variables are used to configure spidev.
* They must be set appropriately before calling
* this function.
* *********************************************************/
static void honeywell_spi_open(t_honeywell_spi *spi, t_symbol *devspi){
int statusVal = 0;
if (strlen(devspi->s_name) == 0) {
spi->spidev = gensym("/dev/spidev0.0");
} else {
spi->spidev = devspi;
}
spi->spifd = open(spi->spidev->s_name, O_RDWR);
if(spi->spifd < 0) {
statusVal = -1;
pd_error(spi, "could not open SPI device");
goto spi_output;
}
statusVal = ioctl (spi->spifd, SPI_IOC_WR_MODE, &(spi->mode));
if(statusVal < 0){
pd_error(spi, "Could not set SPIMode (WR)...ioctl fail");
honeywell_spi_close(spi);
goto spi_output;
}
statusVal = ioctl (spi->spifd, SPI_IOC_RD_MODE, &(spi->mode));
if(statusVal < 0) {
pd_error(spi, "Could not set SPIMode (RD)...ioctl fail");
honeywell_spi_close(spi);
goto spi_output;
}
statusVal = ioctl (spi->spifd, SPI_IOC_WR_BITS_PER_WORD, &(spi->bitsPerWord));
if(statusVal < 0) {
pd_error(spi, "Could not set SPI bitsPerWord (WR)...ioctl fail");
honeywell_spi_close(spi);
goto spi_output;
}
statusVal = ioctl (spi->spifd, SPI_IOC_RD_BITS_PER_WORD, &(spi->bitsPerWord));
if(statusVal < 0) {
pd_error(spi, "Could not set SPI bitsPerWord(RD)...ioctl fail");
honeywell_spi_close(spi);
goto spi_output;
}
statusVal = ioctl (spi->spifd, SPI_IOC_WR_MAX_SPEED_HZ, &(spi->speed));
if(statusVal < 0) {
pd_error(spi, "Could not set SPI speed (WR)...ioctl fail");
honeywell_spi_close(spi);
goto spi_output;
}
statusVal = ioctl (spi->spifd, SPI_IOC_RD_MAX_SPEED_HZ, &(spi->speed));
if(statusVal < 0) {
pd_error(spi, "Could not set SPI speed (RD)...ioctl fail");
honeywell_spi_close(spi);
goto spi_output;
}
spi_output:
if (!statusVal) statusVal = 1;
else statusVal = 0;
outlet_float(spi->x_out4, statusVal);
}
/***********************************************************
* honeywell_spi_close(): Responsible for closing the spidev interface.
* *********************************************************/
static int honeywell_spi_close(t_honeywell_spi *spi){
int statusVal = -1;
if (spi->spifd == -1) {
pd_error(spi, "honeywell_spi: device not open");
return(-1);
}
statusVal = close(spi->spifd);
if(statusVal < 0) {
pd_error(spi, "honeywell_spi: could not close SPI device");
exit(1);
}
outlet_float(spi->x_out4, 0);
spi->spifd = -1;
return(statusVal);
}
/********************************************************************
* This function frees the object (destructor).
* ******************************************************************/
static void honeywell_spi_free(t_honeywell_spi *spi){
if (spi->spifd == 0) {
honeywell_spi_close(spi);
}
}
/********************************************************************
* This function writes data "data" of length "length" to the spidev
* device. Data shifted in from the spidev device is saved back into
* "data".
* ******************************************************************/
static int honeywell_spi_write_read(t_honeywell_spi *spi, unsigned char *data, int length){
struct spi_ioc_transfer spid[length];
int i = 0;
int retVal = -1;
// one spi transfer for each byte
for (i = 0 ; i < length ; i++){
spid[i].tx_buf = (unsigned long)(data + i); // transmit from "data"
spid[i].rx_buf = (unsigned long)(data + i); // receive into "data"
spid[i].len = sizeof(*(data + i));
spid[i].delay_usecs = 0;
spid[i].speed_hz = spi->speed;
spid[i].bits_per_word = spi->bitsPerWord;
spid[i].cs_change = 0;
}
retVal = ioctl(spi->spifd, SPI_IOC_MESSAGE(length), &spid);
if(retVal < 0){
pd_error(spi, "problem transmitting spi data..ioctl");
}
return retVal;
}
/***********************************************************************
* Honeywell HSC Pressure sensor enabled external that by default interacts
* with /dev/spidev0.0 device using
* honeywell_spi_MODE_0 (MODE 0) (defined in linux/spi/spidev.h), speed = 1MHz &
* bitsPerWord=8.
*
* on bang call the spi_write_read function on the a2d object and make sure
* that conversion is configured for single ended conversion on CH0
* i.e. transmit -> byte1 = 0b00000001 (start bit)
* byte2 = 0b1000000 (SGL/DIF = 1, D2=D1=D0=0)
* byte3 = 0b00000000 (Don't care)
* receive -> byte1 = junk
* byte2 = junk + b8 + b9
* byte3 = b7 - b0
*
* after conversion must merge data[1] and data[2] to get final result
* *********************************************************************/
static void honeywell_spi_bang(t_honeywell_spi *spi)
{
if (spi->spifd == -1) {
pd_error(spi, "device not open %d", spi->spifd);
return;
}
uint8_t status = 0;
uint16_t pressure = 0;
uint16_t temperature = 0;
unsigned char data[4]; // four bytes for Honeywell
uint8_t const STATUS_MASK = 0b11000000;
uint16_t const PRESSURE_MASK = 0b0011111111111111;
uint16_t const TEMPERATURE_MASK = 0b1111111111100000;
data[0] = 0b00000000; // we don't send any data to the sensor,
data[1] = 0b00000000; // so just initialise with empty bytes.
data[2] = 0b00000000;
data[3] = 0b00000000;
honeywell_spi_write_read(spi, data, sizeof(data));
// extract vaues from binary data. We have to do bytes separately (unfortunately - maybe there's a better way to access entire con
status = ((uint8_t) data[0] & STATUS_MASK) >> 6;
pressure = (((uint16_t) data[0] << 8) + (uint16_t) data[1]) & PRESSURE_MASK;
temperature = ((((uint16_t) data[2] << 8) + (uint16_t) data[3]) & TEMPERATURE_MASK) >> 5;
outlet_float(spi->x_out1, pressure);
outlet_float(spi->x_out2, temperature);
outlet_float(spi->x_out3, status);
}
/*************************************************
* init function.
* ***********************************************/
static t_honeywell_spi *honeywell_spi_new(t_symbol *devspi){
t_honeywell_spi *spi = (t_honeywell_spi *)pd_new(honeywell_spi_class);
//fprintf(stderr,"devspi<%s>\n", devspi->s_name);
//t_honeywell_spi *a2d = honeywell_spi_new("/dev/spidev0.0", spi_MODE_0, 1000000, 8);
spi->x_out1 = outlet_new(&spi->x_obj, gensym("float"));
spi->x_out2 = outlet_new(&spi->x_obj, gensym("float"));
spi->x_out3 = outlet_new(&spi->x_obj, gensym("float"));
spi->x_out4 = outlet_new(&spi->x_obj, gensym("float"));
spi->spidev = devspi;
spi->mode = SPI_MODE_0;
spi->bitsPerWord = 8;
spi->speed = 1000000;
spi->spifd = -1;
return(spi);
}
void honeywell_spi_setup(void)
{
honeywell_spi_class = class_new(gensym("honeywell_spi"), (t_newmethod)honeywell_spi_new,
(t_method)honeywell_spi_free, sizeof(t_honeywell_spi), 0, A_DEFSYM, 0);
class_addmethod(honeywell_spi_class, (t_method)honeywell_spi_open, gensym("open"),
A_DEFSYM, 0);
class_addmethod(honeywell_spi_class, (t_method)honeywell_spi_close, gensym("close"),
0, 0);
//class_addfloat(honeywell_gpio_class, honeywell_gpio_float); (later do sending data back to the spi)
class_addbang(honeywell_spi_class, honeywell_spi_bang);
}