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/* Copyright (c) 2011 The Chromium OS Authors. All rights reserved.
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
/* ADC module for Chrome EC */
#include "board.h"
#include "console.h"
#include "adc.h"
#include "timer.h"
#include "registers.h"
#include "uart.h"
#include "util.h"
static void configure_gpio(void)
{
volatile uint32_t scratch __attribute__((unused));
/* Enable GPIOE module and delay a few clocks */
LM4_SYSTEM_RCGCGPIO |= 0x0010;
scratch = LM4_SYSTEM_RCGCGPIO;
/* Use analog function for PE3 (AIN0) */
LM4_GPIO_DEN(E) &= ~0x08;
LM4_GPIO_AMSEL(E) |= 0x08;
}
int adc_read(enum adc_channel ch)
{
volatile uint32_t scratch __attribute__((unused));
/* TODO: right now we have only a single channel so this is
* simple. When we have multiple channels, should we...
*
* 1) Read them all using a timer interrupt, and then return
* the most recent value? This is lowest-latency for the
* caller, but won't return accurate data if read frequently.
*
* 2) Reserve SS3 for reading a single value, and configure it
* on each read? Needs mutex if we could have multiple
* callers; doesn't matter if just used for debugging.
*
* 3) Both? */
if (ch != ADC_CH_POT)
return ADC_READ_ERROR;
/* Empty the FIFO of any previous results */
while (!(LM4_ADC_SSFSTAT(0) & 0x100))
scratch = LM4_ADC_SSFIFO(0);
/* Clear the interrupt status */
LM4_ADC_ADCISC |= 0x01;
/* Initiate sample sequence */
LM4_ADC_ADCPSSI |= 0x01;
/* Wait for interrupt */
/* TODO: use a real interrupt */
while (!(LM4_ADC_ADCRIS & 0x01));
/* Read the FIFO */
return LM4_ADC_SSFIFO(0);
}
int adc_read_ec_temperature(void)
{
volatile uint32_t scratch __attribute__((unused));
int a;
/* Empty the FIFO of any previous results */
while (!(LM4_ADC_SSFSTAT(3) & 0x100))
scratch = LM4_ADC_SSFIFO(3);
/* Clear the interrupt status */
LM4_ADC_ADCISC |= 0x08;
/* Initiate sample sequence */
LM4_ADC_ADCPSSI |= 0x08;
/* Wait for interrupt */
/* TODO: use a real interrupt */
/* TODO: timeout */
while (!(LM4_ADC_ADCRIS & 0x08));
/* Read the FIFO and convert to temperature */
a = LM4_ADC_SSFIFO(3);
return 273 + (295 - (225 * 2 * a) / ADC_READ_MAX) / 2;
}
/*****************************************************************************/
/* Console commands */
static int command_adc(int argc, char **argv)
{
uart_printf("ADC POT channel = 0x%03x\n",adc_read(ADC_CH_POT));
return EC_SUCCESS;
}
static int command_ectemp(int argc, char **argv)
{
int t = adc_read_ec_temperature();
uart_printf("EC temperature is %d K = %d C\n", t, t-273);
return EC_SUCCESS;
}
static const struct console_command console_commands[] = {
{"adc", command_adc},
{"ectemp", command_ectemp},
};
static const struct console_group command_group = {
"ADC", console_commands, ARRAY_SIZE(console_commands)
};
/*****************************************************************************/
/* Initialization */
int adc_init(void)
{
volatile uint32_t scratch __attribute__((unused));
/* Enable ADC0 module and delay a few clocks */
LM4_SYSTEM_RCGCADC |= 0x01;
scratch = LM4_SYSTEM_RCGCADC;
/* Configure GPIOs */
configure_gpio();
/* Use external voltage references (VREFA+, VREFA-) instead of
* VDDA and GNDA. */
LM4_ADC_ADCCTL = 0x01;
/* TODO: set up clock using ADCCC register? */
/* Configure sample sequencer 0 */
LM4_ADC_ADCACTSS &= ~0x01;
/* Trigger SS0 by processor request */
LM4_ADC_ADCEMUX = (LM4_ADC_ADCEMUX & 0xfffffff0) | 0x00;
/* Sample AIN0 only */
LM4_ADC_SSMUX(0) = ADC_IN_POT & 0x0f;
LM4_ADC_SSEMUX(0) = (ADC_IN_POT >> 4) & 0x0f;
LM4_ADC_SSCTL(0) = 0x06; /* IE0 | END0 */
/* Enable sample sequencer 0 */
LM4_ADC_ADCACTSS |= 0x01;
/* Configure sample sequencer 3 */
LM4_ADC_ADCACTSS &= ~0x08;
/* Trigger SS3 by processor request */
LM4_ADC_ADCEMUX = (LM4_ADC_ADCEMUX & 0xffffff0f) | 0x00;
/* Sample internal temp sensor */
LM4_ADC_SSMUX(3) = 0x00;
LM4_ADC_SSEMUX(3) = 0x00;
LM4_ADC_SSCTL(3) = 0x0e; /* TS0 | IE0 | END0 */
/* Enable sample sequencer 3 */
LM4_ADC_ADCACTSS |= 0x08;
console_register_commands(&command_group);
return EC_SUCCESS;
}
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