Code to read voltage of battery with ADC of AM335x

Patrick GAMBIER

Prodigy 110 points

Other Parts Discussed in Thread: AM3359, SYSCONFIG

Hi, we connected a battery to the ADC of a AM3359 (via a resistor divider).

Where i can find a simple code source to setup the ADC and to know the voltage of the battery.

I am not using a Linux Kernel, just U-boot.

Regards

over 12 years ago

0 Patrick GAMBIER over 12 years ago

Prodigy 110 points

So, here it is:

In file pll.c

/* ADC clock enable */
__raw_writel(PRCM_MOD_EN, CM_WKUP_ADC_TSC_CLKCTRL);
while (__raw_readl(CM_WKUP_ADC_TSC_CLKCTRL) != PRCM_MOD_EN);

In myapplication.c file

/* Unprotect step registers, TSC_ADC_SS module disabled because configuration in progress */
__raw_writel(0x00000004, TSC_ADC_SS_CTRL);
while((__raw_readl(TSC_ADC_SS_CTRL) & 0x00000001) !=0);
/* No idle mode */
__raw_writel(0x00000004, TSC_ADC_SS_SYSCONFIG);
/* ADC clock 100KHz. Master clock is 24 MHz */
__raw_writel((24000000)/100000, TSC_ADC_SS_ADC_CLKDIV);
/* Enable step 1 (because it is the first one) */
__raw_writel(0x00000002, TSC_ADC_SS_STEPENABLE);
/* VREFN, AIN7, VREFP, Data in FIFO 16 samples average, SW enabled, continuous */
__raw_writel(0x01BFB011, TSC_ADC_SS_STEPCONFIG1);
/* TSC_ADC_SS module enabled */
__raw_writel(0x00000001, TSC_ADC_SS_CTRL);
while((__raw_readl(TSC_ADC_SS_CTRL) & 0x00000001)==0);

/* Wait for a value in FIFO */
tempo=5000; /* 5 msec */
        while((__raw_readl(TSC_ADC_SS_FIFO0COUNT) & 0x7F)==0 && --tempo)
  udelay(1);
if(tempo==0)
  {printf("!!! Error: ADC stuck... in IDLE step ?\n\n");return(-1);}

/* Displays the voltage being given VREFP=1800 mV VREFN=0 */
voltage=(1800*(__raw_readl(TSC_ADC_SS_FIFO0DATA) & 0xFFF))/0xFFF;
printf("Voltage is %d mV\n",voltage);

Defines are

#define ADC_TSC    (PRCM_BASE + 0xD000)

#define CM_WKUP_ADC_TSC_CLKCTRL  (CM_WKUP + 0xBC)/* ADC */

#define TSC_ADC_SS_SYSCONFIG  (ADC_TSC + 0x010)  /* SYSCONFIG   */
#define TSC_ADC_SS_CTRL   (ADC_TSC + 0x040)  /* CTRL        */
#define TSC_ADC_SS_ADC_CLKDIV  (ADC_TSC + 0x04C)  /* ADC_CLKDIV  */
#define TSC_ADC_SS_STEPENABLE  (ADC_TSC + 0x054)  /* STEPENABLE  */
#define TSC_ADC_SS_STEPCONFIG1  (ADC_TSC + 0x064)  /* STEPCONFIG1 */
#define TSC_ADC_SS_FIFO0COUNT  (ADC_TSC + 0x0E4)  /* FIFO0COUNT  */
#define TSC_ADC_SS_FIFO0DATA  (ADC_TSC + 0x100)  /* FIFO0DATA   */

Critics are welcome.

0 do minh quoc over 12 years ago in reply to Patrick GAMBIER

Intellectual 500 points

Sorry I disturb you , If I use kernel , so how to I read ADC ?

0 Patrick GAMBIER over 12 years ago in reply to do minh quoc

Prodigy 110 points

Hi, there is this post with some code. It calls API from Texas Instrument.

http://e2e.ti.com/support/dsp/sitara_arm174_microprocessors/f/791/t/196266.aspx

Regards

0 Radu Donos over 9 years ago in reply to Patrick GAMBIER

Prodigy 130 points

Thanks so much for your code!

I made small changes in your code, now it can be used as a driver (of course with reduced posibilities, just read adc in oneshot mode).

I use u-boot version 3.2 (TI SDK 6), I created folder /drivers/adc/ and put there the following 3 files:

Makefile -> http://pastebin.com/GbxbTwi8

adc_am335x.h -> http://pastebin.com/zTW5WJ9X

adc_am335x.c -> http://pastebin.com/0KBXG5bn

I also changed the Makefile in srcdir, I added the following line:

...

LIBS-y += post/libpost.o

LIBS-y += test/libtest.o

LIBS-y += drivers/adc/libadc.o

...

For PLL I made the following changes:

in file arch/arm/include/asm/arch-am33xx/cpu.h I added:

/* Encapsulating core pll registers */
struct cm_wkuppll {
unsigned int wkclkstctrl; /* offset 0x00 */
...

unsigned int wkup_i2c0ctrl; /* offset 0xB8 */
unsigned int wkup_adc_tsc_ctrl; /* offset 0xBC */
unsigned int resv12[6];
unsigned int divm6dpllcore; /* offset 0xD8 */
};

In file arch/arm/cpu/armv7/am33xx/clock.c I added:

/*
* Enable the peripheral clock for required peripherals
*/
static void enable_per_clocks(void)
{

...

/* ADC clock enable */
writel(PRCM_MOD_EN, &cmwkup->wkup_adc_tsc_ctrl);
while (readl(&cmwkup->wkup_adc_tsc_ctrl) != PRCM_MOD_EN)
;
}

You can include header and use the driver in the following way:

int adc_voltage=am335x_adc_get_voltage(AIN5);
if(adc_voltage<0)
{
	puts("Error reading from ADC!\n");
	return;
}
printf("Battery voltage: %d mV\n", adc_voltage);

0 Michael Sander over 8 years ago in reply to Radu Donos

Prodigy 100 points

I was able to get Radu's code working for u-boot 2013.10 with the following changes:

Instead of changing
arch/arm/cpu/armv7/am33xx/clock.c ,
I added this line:
&cmwkup->wkup_adc_tsc_ctrl,
to
arch/arm/cpu/armv7/am33xx/clock_am33xx.c
function enable_basic_clocks()

My version of u-boot expected makefiles with a capital 'M' and failed with the helpful message:
"No rule to make target .depend"
if you used a makefile with a lowercase 'm'.

Also I moved the prototypes and channel enum from adc_am335x.h into a new file, adc.h in include/asm/arch

Other than those minor changes, it worked out of the box, thanks!

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Code to read voltage of battery with ADC of AM335x