// Example of user space C program to read a humidity and temperature // sensor Sensirion SHT71 (http://www.acmesystems.it/?id=89) // Version improved by by Douglas Gilbert #include #include #include #ifdef __CRIS__ #include "linux/gpio_syscalls.h" #endif // ----------------------------------------------------------------------- // SHT71 sensor define // ----------------------------------------------------------------------- #define CLOCK_BIT 25 // IO line on port G (was OG25) #define DATA_BIT 24 // IO line on port G #define CLOCK_MSK (1 << CLOCK_BIT) #define DATA_MSK (1 << DATA_BIT) #ifdef __CRIS__ // Macro to set the data line direction #define DATA_LINE_IN gpiosetdir(PORTG,DIRIN,DATA_MSK) #define DATA_LINE_OUT gpiosetdir(PORTG,DIROUT,DATA_MSK) #define DATA_LINE_LOW gpiosetdir(PORTG,DIROUT,DATA_MSK);gpioclearbits(PORTG,DATA_MSK) #define DATA_LINE_HIGH gpiosetdir(PORTG,DIRIN,DATA_MSK) #define DATA_LINE_READ gpiogetbits(PORTG,DATA_MSK)?(1):(0) #define CLOCK_LINE_LOW gpioclearbits(PORTG,CLOCK_MSK) #define CLOCK_LINE_HIGH gpiosetbits(PORTG,CLOCK_MSK) #endif #define CMD_READ_TEMP 0x03 #define CMD_READ_HUM 0x05 static int verbose = 0; static const char * version_str = "1.02 20090128"; static void usage(void) { fprintf(stderr, "Usage: " "sht_test [-h] [-r] [-v] [-V]\n" " where:\n" " -h print usage message\n" " -r send reset to SHT before fetching info\n" " -v increase verbosity (more written to log)\n" " -V print version string then exit\n\n" "Test Sensirion SHT-71, CLK=(I)OG%d DATA=IOG%d\n", CLOCK_BIT, DATA_BIT); } #ifdef __CRIS__ // ----------------------------------------------------------------------- // Send the start sequence // ----------------------------------------------------------------------- static void SendStart(void) { DATA_LINE_OUT; CLOCK_LINE_HIGH; usleep(1000); DATA_LINE_IN; DATA_LINE_LOW; CLOCK_LINE_LOW; CLOCK_LINE_HIGH; usleep(1000); DATA_LINE_HIGH; CLOCK_LINE_LOW; DATA_LINE_IN; } // ----------------------------------------------------------------------- // Sensor reset // ----------------------------------------------------------------------- static void SendReset (void) { int k; for (k = 0; k < 12; k++) { CLOCK_LINE_HIGH; usleep(1000); CLOCK_LINE_LOW; } } // ----------------------------------------------------------------------- // Send a byte to the sensor // ----------------------------------------------------------------------- static int SendByte(unsigned char byte) { unsigned char tempbyte; int k; DATA_LINE_OUT; tempbyte = byte; for (k = 0x80; k > 0; k /= 2) { if (tempbyte & k) DATA_LINE_HIGH; else DATA_LINE_LOW; CLOCK_LINE_HIGH; usleep(1000); CLOCK_LINE_LOW; } DATA_LINE_IN; CLOCK_LINE_HIGH; CLOCK_LINE_LOW; return 1; } // ----------------------------------------------------------------------- // Read a byte from the sensor // withack // 1 = send the ACK // 0 = don't send the ACK // ----------------------------------------------------------------------- static unsigned char ReadByte(int withack) { unsigned char tempbyte; int k; tempbyte = 0; DATA_LINE_IN; for (k = 0x80; k > 0; k /= 2) { CLOCK_LINE_HIGH; if (DATA_LINE_READ) tempbyte |= k; CLOCK_LINE_LOW; } if (withack) { // Acknowledge del byte DATA_LINE_OUT; DATA_LINE_LOW; CLOCK_LINE_HIGH; CLOCK_LINE_LOW; DATA_LINE_IN; } else { // Senza acknowledge DATA_LINE_OUT; DATA_LINE_HIGH; CLOCK_LINE_HIGH; CLOCK_LINE_LOW; DATA_LINE_IN; } return tempbyte; } // ---------------------- // Read the temperature // ---------------------- static int ReadTemperature(void) { unsigned char Lsb, Msb, Chk; SendStart(); if (! SendByte(CMD_READ_TEMP)) return 0; while (DATA_LINE_READ) ; Msb = ReadByte(1); if (verbose > 1) fprintf(stderr, "ReadTemperature: Msb=%d\n", Msb); Lsb = ReadByte(1); if (verbose > 1) fprintf(stderr, "ReadTemperature: Lsb=%d\n", Lsb); Chk = ReadByte(0); if (verbose > 1) fprintf(stderr, "ReadTemperature: Chk=%d\n", Chk); if (1 == verbose) fprintf(stderr, "ReadTemperature: Msb=%d Lsb=%d Chk=%d\n", Msb, Lsb, Chk); return (Msb << 8) + Lsb; } // ------------------ // Read the humidity // ------------------ static int ReadHumidity(void) { unsigned char Lsb, Msb, Chk; SendStart(); if (! SendByte(CMD_READ_HUM)) return 0; while (DATA_LINE_READ) ; Msb = ReadByte(1); if (verbose > 1) fprintf(stderr, "ReadHumidity: Msb=%d\n", Msb); Lsb = ReadByte(1); if (verbose > 1) fprintf(stderr, "ReadHumidity: Lsb=%d\n", Lsb); Chk = ReadByte(0); if (verbose > 1) fprintf(stderr, "ReadHumidity: Chk=%d\n", Chk); if (1 == verbose) fprintf(stderr, "ReadHumidity: Msb=%d Lsb=%d Chk=%d\n", Msb, Lsb, Chk); return (Msb << 8) + Lsb ; } #else static int ReadHumidity(void) { return 0; } static int ReadTemperature(void) { return 0; } static void SendReset(void) { } #endif // ---------- // main code // ---------- int main(int argc, char ** argv) { int opt, soh, sot; int do_reset = 0; float rel_humidity, temperature_c; while ((opt = getopt(argc, argv, "hrvV")) != -1) { switch (opt) { case 'h': usage(); exit(EXIT_SUCCESS); case 'r': ++do_reset; break; case 'v': ++verbose; break; case 'V': printf("%s\n", version_str); exit(EXIT_SUCCESS); default: /* '?' */ usage(); exit(EXIT_FAILURE); } } if (optind < argc) { if (optind < argc) { for (; optind < argc; ++optind) fprintf(stderr, "Unexpected extra argument: %s\n", argv[optind]); usage(); exit(EXIT_FAILURE); } } if (verbose) fprintf(stderr, "%s: Clock line (I)OG%d, Data line IOG%d\n", __FILE__ ,CLOCK_BIT, DATA_BIT); if (do_reset > 0) SendReset(); // assume 12 bit (rather than 8 bit) accuracy soh = ReadHumidity(); sot = ReadTemperature(); if (verbose) fprintf(stderr, "soh=%d [0x%x] sot=%d [0x%x]\n", soh, soh, sot, sot); #if 1 // new formula from SHT7x version 4.1 datasheet rel_humidity = -2.0468 + (0.0367 * soh) + (-1.5955E-6 * soh * soh); #else // older formula rel_humidity = -4 + (0.0405 * soh) + -2.8E-6; #endif if (rel_humidity > 99.9) rel_humidity = 100.0; else if (rel_humidity < 0.1) rel_humidity = 0.0; temperature_c = -39.66 + (0.01 * sot); printf ("Rel. Humidity: %.2f %%\n", rel_humidity); printf ("Temperature : %.2f C\n", temperature_c); return 0; }