adding the htu21d.h file

htu21d.h

@@ -0,0 +1,19 @@
+// Gerardo Marx 1/oct/2026
+// HTU21D temperature and humidity sensor library
+// tested in a raspberry pi zero w
+
+#ifndef HTU21D_H
+#define HTU21D_H
+
+// commands and i2c address
+#define ADDR 0x40 //i2c address
+#define HUM 0xE5 // hold master humidity command
+#define TEMP 0xE3
+#define RESET 0xFE
+
+// prototype functions:
+int getTemp(int fd, double *temp);
+
+int getHum(int fd, double *hum);
+
+#endif // THU21D_H