Re: TEMPer and TEMPerHUM usb thermometer driver

[Julian Coleman <jdc%coris.org.uk@localhost>]

Hi,

It looks like we need a different temperature calculation for "sht1x" and
"temper" types.  The attached patch adds the extra sht1x match and also
the "temper" temperature calculation.  With it, I see results like:

  [uthum1]
                 temp:     15.000                                degC
  [uthum3]
                 temp:     17.500                                degC
  [uthum5]
                 temp:     17.630                                degC
    relative humidity:         35

It looks like uthum1 reads low - it would be nice to add some calibration
to envsys for that.  Also, the "temper" types don't appear to report with
as much precision as the "sht1x" types.

It would be good if people oould try this patch and let me know if it works
or if it fails (UTHUM_DEBUG output would be useful here).

Thanks,

J

-- 
  My other computer also runs NetBSD    /        Sailing at Newbiggin
        http://www.netbsd.org/        /   http://www.newbigginsailingclub.org/

Index: src/sys/dev/usb/uthum.c
===================================================================
RCS file: /cvsroot/src/sys/dev/usb/uthum.c,v
retrieving revision 1.4
diff -u -r1.4 uthum.c
--- src/sys/dev/usb/uthum.c     7 Mar 2010 11:28:46 -0000       1.4
+++ src/sys/dev/usb/uthum.c     9 Mar 2010 07:29:38 -0000
@@ -103,7 +103,8 @@
 
 int uthum_read_data(struct uthum_softc *, uint8_t, uint8_t *, size_t, int);
 int uthum_check_sensortype(struct uthum_softc *);
-int uthum_sht1x_temp(unsigned int);
+int uthum_temper_temp(uint8_t, uint8_t);
+int uthum_sht1x_temp(uint8_t, uint8_t);
 int uthum_sht1x_rh(unsigned int, int);
 
 void uthum_intr(struct uhidev *, void *, u_int);
@@ -297,8 +298,10 @@
 uthum_check_sensortype(struct uthum_softc *sc)
 {
        uint8_t buf[8];
-       static uint8_t sht1x_sig[] =
+       static uint8_t sht1x_sig0[] =
            { 0x57, 0x5a, 0x13, 0x00, 0x14, 0x00, 0x53, 0x00 };
+       static uint8_t sht1x_sig1[] =
+           { 0x57, 0x5a, 0x14, 0x00, 0x14, 0x00, 0x53, 0x00 };
        static uint8_t temper_sig[] =
            { 0x57, 0x58, 0x14, 0x00, 0x14, 0x00, 0x53, 0x00 };
 
@@ -312,10 +315,16 @@
         * therefore, compare full bytes.
         * TEMPerHUM HID (SHT1x version) will return:
         *   { 0x57, 0x5a, 0x13, 0x00, 0x14, 0x00, 0x53, 0x00 }
-        * TEMPer HID (SHT1x version) will return:
+        *   { 0x57, 0x5a, 0x14, 0x00, 0x14, 0x00, 0x53, 0x00 }
+        * TEMPer HID (TEMPer version) will return:
         *   { 0x57, 0x58, 0x14, 0x00, 0x14, 0x00, 0x53, 0x00 }
         */
-       if (0 == memcmp(buf, sht1x_sig, sizeof(sht1x_sig)))
+       DPRINTF(("uthum: device signature: "
+           "0x%0x 0x%0x 0x%0x 0x%0x 0x%0x 0x%0x 0x%0x 0x%0x\n",
+           buf[0], buf[1], buf[2], buf[3], buf[4], buf[5], buf[6], buf[7]));
+       if (0 == memcmp(buf, sht1x_sig0, sizeof(sht1x_sig0)))
+               return UTHUM_TYPE_SHT1x;
+       if (0 == memcmp(buf, sht1x_sig1, sizeof(sht1x_sig1)))
                return UTHUM_TYPE_SHT1x;
        if (0 == memcmp(buf, temper_sig, sizeof(temper_sig)))
                return UTHUM_TYPE_TEMPER;
@@ -329,7 +338,7 @@
 {
        struct uthum_softc *sc = sme->sme_cookie;
        uint8_t buf[8];
-       unsigned int temp_tick, humidity_tick;
+       unsigned int humidity_tick;
        int temp, rh;
 
        switch (sc->sc_sensortype) {
@@ -340,11 +349,14 @@
                        sc->sc_sensor[UTHUM_HUMIDITY].state = ENVSYS_SINVALID;
                        return;
                }
+               DPRINTF(("%s: read SHT1x data "
+                   "0x%0x 0x%0x 0x%0x 0x%0x 0x%0x 0x%0x 0x%0x 0x%0x\n",
+                   sc->sc_sme->sme_name, buf[0], buf[1], buf[2], buf[3],
+                   buf[4], buf[5], buf[6], buf[7]));
 
-               temp_tick = (buf[0] * 256 + buf[1]) & 0x3fff;
                humidity_tick = (buf[2] * 256 + buf[3]) & 0x0fff;
 
-               temp = uthum_sht1x_temp(temp_tick);
+               temp = uthum_sht1x_temp(buf[0], buf[1]);
                rh = uthum_sht1x_rh(humidity_tick, temp);
 
                sc->sc_sensor[UTHUM_HUMIDITY].value_cur = rh / 1000;
@@ -356,8 +368,11 @@
                        sc->sc_sensor[UTHUM_TEMP].state = ENVSYS_SINVALID;
                        return;
                }
-               temp_tick = (buf[0] * 256 + buf[1]) & 0xffff;
-               temp = uthum_sht1x_temp(temp_tick);
+               DPRINTF(("%s: read TEMPER data "
+                   "0x%0x 0x%0x 0x%0x 0x%0x 0x%0x 0x%0x 0x%0x 0x%0x\n",
+                   sc->sc_sme->sme_name, buf[0], buf[1], buf[2], buf[3],
+                   buf[4], buf[5], buf[6], buf[7]));
+               temp = uthum_temper_temp(buf[0], buf[1]);
                break;
        default:
                /* do nothing */
@@ -370,9 +385,26 @@
 
 /* return C-degree * 100 value */
 int
-uthum_sht1x_temp(unsigned int ticks)
+uthum_temper_temp(uint8_t msb, uint8_t lsb)
 {
-       return (ticks - 4010);
+       int val;
+
+       val = (msb << 8) | lsb;
+       if (val >= 32768) {
+               val = val - 65536;
+       }
+       val = (val * 100) >> 8;
+       return val;
+}
+
+/* return C-degree * 100 value */
+int
+uthum_sht1x_temp(uint8_t msb, uint8_t lsb)
+{
+       int val;
+
+       val = ((msb << 8) + lsb) - 4096;
+       return val;
 }
 
 /* return %RH * 1000 */