ADC overo 2.6.38-

2012-01-10T15:19:18Z

Bart: fixed some bugs in the example program

For overo's running kernel 2.6.38 and earlier

Use /dev/twl4030 to access the adc's

See Scott Ellis' page

http://www.jumpnowtek.com/index.php?option=com_content&view=article&id=79&Itemid=91

The source code uses the ‘twl4030’ as a name - which is also an older chip from TI. The TPS65950 on the OMAP board is pin-compatible and uses the same/similar ADC module so the older code works nicely (no need to reinvent the wheel).

You can support the ‘twl4030’ in Linux is via a kernel module, which is the way you can access it directly via /dev/twl4030. The TPS65950 talks to the OMAP chip via I2C bus.

Save both files in the same directory then build

twl4030-madc.h

/*
* include/linux/i2c/twl4030-madc.h
*
* TWL4030 MADC module driver header
*
* Copyright (C) 2008 Nokia Corporation
* Mikko Ylinen <mikko.k.ylinen@...>
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* version 2 as published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
* 02110-1301 USA
*
*/
#ifndef _TWL4030_MADC_H
#define _TWL4030_MADC_H
struct twl4030_madc_conversion_method {
u8 sel;
u8 avg;
u8 rbase;
u8 ctrl;
};
#define TWL4030_MADC_MAX_CHANNELS 16
struct twl4030_madc_request {
u16 channels;
u16 do_avg;
u16 method;
u16 type;
int active;
int result_pending;
int rbuf[TWL4030_MADC_MAX_CHANNELS];
void (*func_cb)(int len, int channels, int *buf);
};
enum conversion_methods {
TWL4030_MADC_RT,
TWL4030_MADC_SW1,
TWL4030_MADC_SW2,
TWL4030_MADC_NUM_METHODS
};
enum sample_type {
TWL4030_MADC_WAIT,
TWL4030_MADC_IRQ_ONESHOT,
TWL4030_MADC_IRQ_REARM
};
#define TWL4030_MADC_CTRL1 0x00
#define TWL4030_MADC_CTRL2 0x01
#define TWL4030_MADC_RTSELECT_LSB 0x02
#define TWL4030_MADC_SW1SELECT_LSB 0x06
#define TWL4030_MADC_SW2SELECT_LSB 0x0A
#define TWL4030_MADC_RTAVERAGE_LSB 0x04
#define TWL4030_MADC_SW1AVERAGE_LSB 0x08
#define TWL4030_MADC_SW2AVERAGE_LSB 0x0C
#define TWL4030_MADC_CTRL_SW1 0x12
#define TWL4030_MADC_CTRL_SW2 0x13
#define TWL4030_MADC_RTCH0_LSB 0x17
#define TWL4030_MADC_GPCH0_LSB 0x37
#define TWL4030_MADC_MADCON (1<<0) /* MADC power on */
#define TWL4030_MADC_BUSY (1<<0) /* MADC busy */
#define TWL4030_MADC_EOC_SW (1<<1) /* MADC conversion completion */
#define TWL4030_MADC_SW_START (1<<5) /* MADC SWx start conversion */
#define TWL4030_MADC_ADCIN0 (1<<0)
#define TWL4030_MADC_ADCIN1 (1<<1)
#define TWL4030_MADC_ADCIN2 (1<<2)
#define TWL4030_MADC_ADCIN3 (1<<3)
#define TWL4030_MADC_ADCIN4 (1<<4)
#define TWL4030_MADC_ADCIN5 (1<<5)
#define TWL4030_MADC_ADCIN6 (1<<6)
#define TWL4030_MADC_ADCIN7 (1<<7)
#define TWL4030_MADC_ADCIN8 (1<<8)
#define TWL4030_MADC_ADCIN9 (1<<9)
#define TWL4030_MADC_ADCIN10 (1<<10)
#define TWL4030_MADC_ADCIN11 (1<<11)
#define TWL4030_MADC_ADCIN12 (1<<12)
#define TWL4030_MADC_ADCIN13 (1<<13)
#define TWL4030_MADC_ADCIN14 (1<<14)
#define TWL4030_MADC_ADCIN15 (1<<15)
/* Fixed channels */
#define TWL4030_MADC_BTEMP TWL4030_MADC_ADCIN1
#define TWL4030_MADC_VBUS TWL4030_MADC_ADCIN8
#define TWL4030_MADC_VBKB TWL4030_MADC_ADCIN9
#define TWL4030_MADC_ICHG TWL4030_MADC_ADCIN10
#define TWL4030_MADC_VCHG TWL4030_MADC_ADCIN11
#define TWL4030_MADC_VBAT TWL4030_MADC_ADCIN12
/* BCI related - XXX To be moved elsewhere */
#define TWL4030_BCI_BCICTL1 0x23
#define TWL4030_BCI_MESBAT (1<<1)
#define TWL4030_BCI_TYPEN (1<<4)
#define TWL4030_BCI_ITHEN (1<<3)
#define TWL4030_MADC_IOC_MAGIC '`'
#define TWL4030_MADC_IOCX_ADC_RAW_READ _IO(TWL4030_MADC_IOC_MAGIC, 0)
struct twl4030_madc_user_parms {
int channel;
int average;
int status;
u16 result;
};
int twl4030_madc_conversion(struct twl4030_madc_request *conv);
#endif

'''Main program'''

/* Test code for the MADC function
*
* Hugo Vincent, May 2009
*/
#include <sys/ioctl.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdint.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <time.h>
typedef uint8_t u8;
typedef uint16_t u16;
#include "twl4030-madc.h"
/* Note: (very weird) the madc driver seems to crash if you've got driver debugging
* turned on in your defconfig... */
/* Channel numbering:
* ADC0-1 : to do with battery charging, not relevant on Overo
* ADC2-7 : general purpose, input range = 0 - 2.5V.
* On Overo, ADC2 seems to read as ~0.4 and ADC7 as ~1.4V (?).
* ADC8 : USB OTG port bus voltage.
* ADC9-11 : more battery charging stuff, not relevant.
* ADC12 : main battery voltage.
* This will be the system 3.3V rail in our case
* ADC13-15: reserved or not relevant.
*/
struct adc_channel {
int number;
char name[16];
float input_range;
};
struct adc_channel channels[] = {
{
.number = 2,
.name = "ADCIN2",
.input_range = 2.5,
},
{
.number = 3,
.name = "ADCIN3",
.input_range = 2.5,
},
{
.number = 4,
.name = "ADCIN4",
.input_range = 2.5,
},
{
.number = 5,
.name = "ADCIN5",
.input_range = 2.5,
},
{
.number = 6,
.name = "ADCIN6",
.input_range = 2.5,
},
{
.number = 7,
.name = "ADCIN7",
.input_range = 2.5,
},
{
.number = 8,
.name = "VBUS_USB_OTG",
.input_range = 7.0,
},
{
.number = 12,
.name = "VBATT/3.3V_RAIL",
.input_range = 6.0,
},
};
int main(int argc, char **argv)
{
int d = open("/dev/twl4030-madc", O_RDWR | O_NONBLOCK);
if (d == -1)
{
printf("could not open device /dev/twl4030-madc \n");
exit(EXIT_FAILURE);
}
struct twl4030_madc_user_parms *par;
par = malloc(sizeof(struct twl4030_madc_user_parms));
int j;
for (j = 0; j < (sizeof(channels)/sizeof(struct adc_channel)); j++)
{
memset(par, 0, sizeof(struct twl4030_madc_user_parms));
par->channel = channels[j].number;
int ret = ioctl(d, TWL4030_MADC_IOCX_ADC_RAW_READ, par);
float result = ((unsigned int)par->result) / 1024.f;/* 10 bit ADC -> 1024 */
if (ret == 0 && par->status != -1)
{
printf("%s (channel %d): %f\n", channels[j].name, channels[j].number,result * channels[j].input_range);
}
else
{
if (par->status == -1)
{
printf("Channel %d (%s) timed out!\n", j, channels[j].name);
printf("ERROR\n");
exit(EXIT_FAILURE);
}
}
}
return 0;
}

compile it

gcc –o madc madc.c

root@overo:~# ./madc
ADCIN2 (channel 2): 0.673828
ADCIN3 (channel 3): 0.087891
ADCIN4 (channel 4): 0.612793
ADCIN5 (channel 5): 0.090332
ADCIN6 (channel 6): 0.341797
ADCIN7 (channel 7): 1.374512
VBUS_USB_OTG (channel 8): 5.154297
VBATT/3.3V_RAIL (channel 12): 3.275391
root@overo:~#

when using the ADCs you may/will need to scale values.
To connect up circuits running at higher than 2.5V you will need to use a voltage divider (resistors)

Vincent, H. (2009) ADC Code Example – Help with Overo ADC. http://old.nabble.com/Re%3A-Help-with-Overo-ADC-td24174607.html

TI TPS65950 Integrated Power Management/Audio Codec Data Manual http://focus.ti.com/lit/ds/symlink/tps65950.pdf

TI TPS65950 OMAP Power Management and System Companion Device Version G Technical Reference Manual http://focus.ti.com/lit/ug/swcu050g/swcu050g.pdf

Gumstix User Wiki - User contributions [en]

ADC overo 2.6.38-