Diff: si7021.cpp

Revision:

0:9909c9c7d326

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/si7021.cpp	Tue Sep 12 17:17:03 2017 +0000
@@ -0,0 +1,80 @@
+#include "si7021.h"
+
+#define SI7021A20_I2C_ADDR              0x80
+
+#define SI7021A20_CMD_MEAS_RH_HMM       0xE5
+#define SI7021A20_CMD_MEAS_RH_NHMM      0xF5
+#define SI7021A20_CMD_MEAS_TEMP_HMM     0xE3
+#define SI7021A20_CMD_MEAS_TEMP_NHMM    0xF3
+#define SI7021A20_CMD_READ_TEMP         0xE0
+#define SI7021A20_CMD_RESET             0xFE
+#define SI7021A20_CMD_WRITE_USER1       0xE6
+#define SI7021A20_CMD_WRITE_USER2       0xE7
+#define SI7021A20_CMD_WRITE_HEAT_CTRL   0x51
+#define SI7021A20_CMD_READ_HEAT_CTRL    0x11
+#define SI7021A20_CMD_READ_ID1          0xFA0F
+#define SI7021A20_CMD_READ_ID2          0xFCC9
+#define SI7021A20_REGF_ID2_DEV_ID               0x15
+#define SI7021A20_CMD_READ_FW_REV       0x84B8
+
+bool SI7021::_i2c_transfer(int address, void * buff, size_t write_size, size_t read_size)
+{
+    bool ok;
+    bool expect_response = (read_size != 0);
+    
+    ok = !_i2c->write(address, (char*)buff, write_size, expect_response);
+    if (ok && expect_response)
+        ok = !_i2c->read(address, (char*)buff, read_size);
+
+    return ok;
+}
+
+/*
+bool SI7021::_validate(void)
+{
+    bool    ok;
+    uint8_t buff[4];
+
+    buff[0] = (uint8_t)(SI7021A20_CMD_READ_ID2 >> 8);
+    buff[1] = (uint8_t)(SI7021A20_CMD_READ_ID2);
+    
+    ok = (i2c_transfer(SI7021A20_I2C_ADDR, buff, 2, 1)) &&
+         (SI7021A20_REGF_ID2_DEV_ID == buff[0]);
+    
+    return ok;
+}
+*/
+
+bool SI7021::read(si7021_measurements_t * data) {
+    bool    ok;
+    union {
+        char    cmd;
+        struct {
+            uint8_t  meas_msb;
+            uint8_t  meas_lsb;
+        };
+    } buff;
+
+    buff.cmd = SI7021A20_CMD_MEAS_RH_HMM;
+    ok = (_i2c_transfer(SI7021A20_I2C_ADDR, &buff, 1, 2));
+    if (ok) {
+        // Humidity% = measurement * 125/65536 - 6
+        int meas_raw        = ((int)buff.meas_msb << 8) + buff.meas_lsb;
+        data->humidity_PR   = (float)meas_raw * (125.0F/65536.0F) - 6.0F;
+//        data->humidity      = meas_raw / 2 - 1573;
+//        data->humidity_norm = 262;
+//        printf("<humidityH/r = %f/%d>", Humidity, meas_raw);
+            
+        buff.cmd = SI7021A20_CMD_READ_TEMP;
+        ok = _i2c_transfer(SI7021A20_I2C_ADDR, &buff, 1, 2);
+    }
+    if (ok) {
+        // TempC = measurement * 175.72/65536 - 46.85
+        int meas_raw    = ((int)buff.meas_msb << 8) + buff.meas_lsb;
+        data->temp_C    = meas_raw * (175.72/65536.0) - 46.85;
+//        data->temp      = meas_raw / 2 - 8736;
+//        data->temp_norm = 186;
+//        printf("<tempC/F/r = %f/%f/%d>", Temp, Temp * 9 / 5 + 32, meas_raw);
+    }
+    return ok;
+}