diff options
Diffstat (limited to 'sys/dev/gpio')
| -rw-r--r-- | sys/dev/gpio/gpioths.c | 55 |
1 files changed, 49 insertions, 6 deletions
diff --git a/sys/dev/gpio/gpioths.c b/sys/dev/gpio/gpioths.c index a4267b76359f..cb2d754d979e 100644 --- a/sys/dev/gpio/gpioths.c +++ b/sys/dev/gpio/gpioths.c @@ -47,6 +47,14 @@ __FBSDID("$FreeBSD$"); * This is driver for Temperature & Humidity sensor which provides digital * output over single-wire protocol from embedded 8-bit microcontroller. * + * This driver supports the following chips: + * DHT11: Temp 0c to 50c +-2.0c, Humidity 20% to 90% +-5% + * DHT12: Temp -20c to 60c +-0.5c, Humidity 20% to 95% +-5% + * DHT21: Temp -40c to 80c +-0.3c, Humidity 0% to 100% +-3% + * DHT22: Temp -40c to 80c +-0.3c, Humidity 0% to 100% +-2% + * AM2301: Same as DHT21, but also supports i2c interface. + * AM2302: Same as DHT22, but also supports i2c interface. + * * Temp/Humidity sensor can't be discovered automatically, please specify hints * as part of loader or kernel configuration: * hint.gpioths.0.at="gpiobus0" @@ -59,8 +67,6 @@ __FBSDID("$FreeBSD$"); #define GPIOTHS_DHT_TIMEOUT 1000 /* 1ms = 1000us */ #define GPIOTHS_DHT_CYCLES 41 #define GPIOTHS_DHT_ONEBYTEMASK 0xFF -#define GPIOTHS_DHT_TEMP_SHIFT 8 -#define GPIOTHS_DHT_HUM_SHIFT 24 struct gpioths_softc { device_t dev; @@ -160,7 +166,7 @@ gpioths_dht_readbytes(device_t bus, device_t dev) uint32_t intervals[GPIOTHS_DHT_CYCLES]; uint32_t err, avglen, value; uint8_t crc, calc; - int i, offset, size; + int i, negmul, offset, size, tmphi, tmplo; sc = device_get_softc(dev); @@ -246,9 +252,46 @@ gpioths_dht_readbytes(device_t bus, device_t dev) goto error; } + /* + * For DHT11/12, the values are split into 8 bits of integer and 8 bits + * of fractional tenths. On DHT11 the fraction bytes are always zero. + * On DHT12 the sign bit is in the high bit of the fraction byte. + * - DHT11: 0HHHHHHH 00000000 00TTTTTT 00000000 + * - DHT12: 0HHHHHHH 0000hhhh 00TTTTTT s000tttt + * + * For DHT21/21, the values are are encoded in 16 bits each, with the + * temperature sign bit in the high bit. The values are tenths of a + * degree C and tenths of a percent RH. + * - DHT21: 000000HH HHHHHHHH s00000TT TTTTTTTT + * - DHT22: 000000HH HHHHHHHH s00000TT TTTTTTTT + * + * For all devices, some bits are always zero because of the range of + * values supported by the device. + * + * We figure out how to decode things based on the high byte of the + * humidity. A DHT21/22 cannot report a value greater than 3 in + * the upper bits of its 16-bit humidity. A DHT11/12 should not report + * a value lower than 20. To allow for the possibility that a device + * could report a value slightly out of its sensitivity range, we split + * the difference and say if the value is greater than 10 it cannot be a + * DHT22 (that would be a humidity over 256%). + */ +#define DK_OFFSET 2731 /* Offset between K and C, in decikelvins. */ + if ((value >> 24) > 10) { + /* DHT11 or DHT12 */ + tmphi = (value >> 8) & 0x3f; + tmplo = value & 0x0f; + negmul = (value & 0x80) ? -1 : 1; + sc->temp = DK_OFFSET + (negmul * (tmphi * 10 + tmplo)); + sc->hum = (value >> 24) & 0x7f; + } else { + /* DHT21 or DHT22 */ + negmul = (value & 0x8000) ? -1 : 1; + sc->temp = DK_OFFSET + (negmul * (value & 0x03ff)); + sc->hum = ((value >> 16) & 0x03ff) / 10; + } + sc->fails = 0; - sc->temp = (value >> GPIOTHS_DHT_TEMP_SHIFT) & GPIOTHS_DHT_ONEBYTEMASK; - sc->hum = (value >> GPIOTHS_DHT_HUM_SHIFT) & GPIOTHS_DHT_ONEBYTEMASK; #ifdef GPIOTHS_DEBUG /* Debug bits */ @@ -296,7 +339,7 @@ gpioths_attach(device_t dev) sysctl_add_oid(ctx, SYSCTL_CHILDREN(tree), OID_AUTO, "temperature", \ CTLFLAG_RD | CTLTYPE_INT | CTLFLAG_MPSAFE, - &sc->temp, 0, sysctl_handle_int, "I", "temperature", NULL); + &sc->temp, 0, sysctl_handle_int, "IK", "temperature", NULL); SYSCTL_ADD_INT(ctx, SYSCTL_CHILDREN(tree), OID_AUTO, "humidity", CTLFLAG_RD, &sc->hum, 0, "relative humidity(%)"); |