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drivers/dht: optimized driver code

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- simplyfied pulse parsing code
- inlined one-time called functions
- some style fixes
This commit is contained in:
Hauke Petersen 2016-01-21 17:22:28 +01:00
parent f5f793c3f2
commit 044cb3c2f9
1 changed files with 58 additions and 88 deletions
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146
drivers/dht/dht.c
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@ -34,57 +34,37 @@
#include "dht.h"
#include "dht_params.h"
#define ENABLE_DEBUG (0)
#define ENABLE_DEBUG (1)
#include "debug.h"
/***********************************************************************
* internal API declaration
**********************************************************************/
static int dht_test_checksum(uint32_t data, uint8_t checksum);
void dht_parse_11(dht_data_t *data, float *outhum, float *outtemp);
void dht_parse_22(dht_data_t *data, float *outhum, float *outtemp);
/***********************************************************************
* internal API implementation
**********************************************************************/
void dht_parse_11(dht_data_t *data, float *outhum, float *outtemp)
{
*outhum = data->humidity >> 8;
*outtemp = data->temperature >> 8;
}
void dht_parse_22(dht_data_t *data, float *outhum, float *outtemp)
{
*outhum = data->humidity / 10;
/* the highest bit indicates a negative value */
if (data->temperature & 0x8000) {
*outtemp = (data->temperature & 0x7FFF) / -10;
}
else {
*outtemp = data->temperature / 10;
}
}
static int dht_test_checksum(uint32_t data, uint8_t checksum)
{
uint8_t sum;
sum = (data >> 0) & 0x000000FF;
sum += (data >> 8) & 0x000000FF;
sum += (data >> 16) & 0x000000FF;
sum += (data >> 24) & 0x000000FF;
return ((checksum == sum) && (checksum != 0));
}
/***********************************************************************
* public API implementation
**********************************************************************/
#define PULSE_WIDTH_THRESHOLD (40U)
/**
* @brief Allocation of memory for device descriptors
*/
dht_t dht_devs[DHT_NUMOF];
static uint16_t read(gpio_t pin, int bits)
{
uint32_t start, end;
uint16_t res = 0;
for (int i = 0; i < bits; i++) {
res <<= 1;
/* measure the length between the next rising and falling flanks (the
* time the pin is high - smoke up :-) */
while (!gpio_read(pin));
start = xtimer_now();
while (gpio_read(pin));
end = xtimer_now();
/* if the high phase was more than 40us, we got a 1 */
if ((end - start) > PULSE_WIDTH_THRESHOLD) {
res |= 0x0001;
}
}
return res;
}
void dht_auto_init(void)
{
for (unsigned i = 0; i < DHT_NUMOF; i++) {
@ -111,10 +91,10 @@ int dht_init(dht_t *dev, const dht_params_t *params)
return 0;
}
int dht_read_raw(dht_t *dev, dht_data_t *outdata)
int dht_read_raw(dht_t *dev, dht_data_t *data)
{
uint32_t data;
uint8_t checksum;
uint8_t csum, sum;
uint16_t hum, temp;
/* send init signal to device */
gpio_clear(dev->pin);
@ -133,59 +113,49 @@ int dht_read_raw(dht_t *dev, dht_data_t *outdata)
* [humidity][temperature][checksum]
*/
/* read all the bits */
uint64_t les_bits = 0x00000000000000;
for (int c = 0; c < 40; c++) {
les_bits <<= 1; /* this is a nop in the first iteration, but
we must not shift the last bit */
/* wait for start of bit */
while (!gpio_read(dev->pin)) ;
unsigned long start = xtimer_now();
/* wait for end of bit */
while (gpio_read(dev->pin)) ;
/* calculate bit length (long 1, short 0) */
unsigned long stop = xtimer_now();
/* compensate for overflow if needed */
if (stop < start) {
stop = UINT32_MAX - stop;
start = 0;
}
if ((stop - start) > 40) {
/* read 1, set bit */
les_bits |= 0x0000000000000001;
}
else {
/* read 0, don't set bit */
}
}
checksum = les_bits & 0x00000000000000FF;
data = (les_bits >> 8) & 0x00000000FFFFFFFF;
/* read the humidity, temperature, and checksum bits */
hum = read(dev->pin, 16);
temp = read(dev->pin, 16);
csum = (uint8_t)read(dev->pin, 8);
/* set pin high again - so we can trigger the next reading by pulling it low
* again */
gpio_init(dev->pin, GPIO_DIR_OUT, dev->pull);
gpio_set(dev->pin);
/* check checksum */
int ret = dht_test_checksum(data, checksum);
if (!ret) {
DEBUG("checksum fail\n");
/* parse the RAW values */
DEBUG("RAW: temp: %7i hum: %7i\n", (int)temp, (int)hum);
data->humidity = hum;
data->temperature = temp;
/* and finally validate the checksum */
sum = (temp >> 8) + (temp & 0xff) + (hum >> 8) + (hum & 0xff);
if ((sum != csum) || (csum == 0)) {
DEBUG("error: checksum invalid\n");
return -1;
}
outdata->humidity = data >> 16;
outdata->temperature = data & 0x0000FFFF;
return (ret - 1); /* take that logic! */
return 0;
}
void dht_parse(dht_t *dev, dht_data_t *data, float *outrelhum, float *outtemp)
{
switch (dev->type) {
case (DHT11):
dht_parse_11(data, outrelhum, outtemp);
case DHT11:
*outrelhum = data->humidity >> 8;
*outtemp = data->temperature >> 8;
break;
case DHT22:
dht_parse_22(data, outrelhum, outtemp);
*outrelhum = data->humidity / 10;
/* the highest bit indicates a negative value */
if (data->temperature & 0x8000) {
*outtemp = (data->temperature & 0x7FFF) / -10;
}
else {
*outtemp = data->temperature / 10;
}
break;
default: