Joseph Ellsworth / Mbed 2 deprecated xj-Nucleo-F303K8-SHT75-TEST

Testing SHT75 humidity sensor on STM F303K8 board.

Dependencies:   SHT75 mbed

Fork of Nucleo-F303K8-SSD1306_OLED by Joseph Ellsworth

Sample code to test SHT75 humidity sensor using STM F303K8 board. Uses a 3.3V from board to power sensor. 10K resistor Pull-up on data. Must not be on same pins as I2C. Uses D0 for Clk and D1 for Data.

I had to modify sample code supplied by https://developer.mbed.org/users/nimbusgb/code/SHT75/ because the sensor failed to read without the softReset() and readStatus() at beginning of measurement loop. I think this is caused by the 72Mhtz speed of the F303K8 but did not attempt to fully diagnose.

The readStatus() method from library seems to malfunction and always return a -1 which never changes even when sensor is unplugged.

See https://www.sensirion.com/fileadmin/user_upload/customers/sensirion/Dokumente/Humidity_Sensors/Sensirion_Humidity_Sensors_SHT7x_Datasheet_V5.pdf section 2.1 for wiring.

main.cpp@5:4b66dfbc52a5, 2016-07-27 (annotated)

Committer:
joeata2wh
Date:
Wed Jul 27 19:54:51 2016 +0000
Revision:
5:4b66dfbc52a5
Parent:
4:2c46c3bc8032 
updated comments

Who changed what in which revision?

UserRevisionLine numberNew contents of line
joeata2wh 5:4b66dfbc52a5 1 /* Test ability to read SHT75 sensor from F303K8 board.
joeata2wh 5:4b66dfbc52a5 2
joeata2wh 4:2c46c3bc8032 3 Note: Can not be on same pins as I2C due to different pull up
joeata2wh 4:2c46c3bc8032 4 requirements.
joeata2wh 2:dc3e84d595c3 5
joeata2wh 3:47148198f5f2 6 By Joseph Ellsworth CTO of A2WH
joeata2wh 3:47148198f5f2 7 Take a look at A2WH.com Producing Water from Air using Solar Energy
joeata2wh 4:2c46c3bc8032 8 March-2016 License: https://developer.mbed.org/handbook/MIT-Licence
joeata2wh 3:47148198f5f2 9 Please contact us http://a2wh.com for help with custom design projects.
joeata2wh 5:4b66dfbc52a5 10
joeata2wh 5:4b66dfbc52a5 11 Sample code to test SHT75 humidity sensor using STM F303K8 board.
joeata2wh 5:4b66dfbc52a5 12 Uses a 3.3V from board to power sensor. 10K resistor Pull-up on data.
joeata2wh 5:4b66dfbc52a5 13 Must not be on same pins as I2C. Uses D0 for Clk and D1 for Data.
joeata2wh 3:47148198f5f2 14
joeata2wh 5:4b66dfbc52a5 15 I had to modify sample code supplied by https://developer.mbed.org/users/nimbusgb/code/SHT75/
joeata2wh 5:4b66dfbc52a5 16 because the sensor failed to read without the softReset() and readStatus() at beginning
joeata2wh 5:4b66dfbc52a5 17 of measurement loop. I think this is caused by the 72Mhtz speed of the F303K8 but did
joeata2wh 5:4b66dfbc52a5 18 not attempt to fully diagnose.
joeata2wh 5:4b66dfbc52a5 19
joeata2wh 5:4b66dfbc52a5 20 The readStatus() method from library seems to malfunction and always return a -1
joeata2wh 5:4b66dfbc52a5 21 which never changes even when sensor is unplugged.
joeata2wh 5:4b66dfbc52a5 22
joeata2wh 3:47148198f5f2 23
joeata2wh 1:90d213185462 24 */
joeata2wh 0:fa185766e039 25
joeata2wh 0:fa185766e039 26 #include "mbed.h"
joeata2wh 4:2c46c3bc8032 27 #include <stdint.h>
joeata2wh 2:dc3e84d595c3 28
joeata2wh 4:2c46c3bc8032 29 #define sht75_clk D0
joeata2wh 4:2c46c3bc8032 30 #define sht75_data D1
joeata2wh 4:2c46c3bc8032 31 #include "sht7X.h"
joeata2wh 4:2c46c3bc8032 32 SHT75 sht(sht75_clk, sht75_data);
joeata2wh 4:2c46c3bc8032 33
joeata2wh 2:dc3e84d595c3 34
joeata2wh 2:dc3e84d595c3 35 // Host PC Communication channels
joeata2wh 2:dc3e84d595c3 36 Serial pc(USBTX, USBRX); // tx, rx
joeata2wh 4:2c46c3bc8032 37 char buff[100];
joeata2wh 2:dc3e84d595c3 38
joeata2wh 0:fa185766e039 39 DigitalOut myled(LED1);
joeata2wh 2:dc3e84d595c3 40
joeata2wh 2:dc3e84d595c3 41 int main()
joeata2wh 2:dc3e84d595c3 42 {
joeata2wh 4:2c46c3bc8032 43 pc.baud(38400);
joeata2wh 4:2c46c3bc8032 44 wait(1);
joeata2wh 0:fa185766e039 45 while(1) {
joeata2wh 2:dc3e84d595c3 46 myled = !myled;
joeata2wh 4:2c46c3bc8032 47 float temperature; // temperature -40 to 120 deg C
joeata2wh 4:2c46c3bc8032 48 float humidity; // relative humidity 1% to 100%
joeata2wh 4:2c46c3bc8032 49 float humi_f,rh_lin,rh_true; // working registers for Illustration purposes
joeata2wh 4:2c46c3bc8032 50 int t; // temporary store for the temp ticks
joeata2wh 4:2c46c3bc8032 51 int h;
joeata2wh 4:2c46c3bc8032 52 sht.softReset();
joeata2wh 4:2c46c3bc8032 53 int stat = sht.readStatus();
joeata2wh 4:2c46c3bc8032 54 wait(3.0);
joeata2wh 4:2c46c3bc8032 55 sht.readTempTicks(&t);
joeata2wh 4:2c46c3bc8032 56 temperature = ((float)(t) * 0.01) - 39.61;
joeata2wh 3:47148198f5f2 57
joeata2wh 4:2c46c3bc8032 58 sht.readHumidityTicks(&h);
joeata2wh 4:2c46c3bc8032 59 humi_f = (float)(h);
joeata2wh 4:2c46c3bc8032 60 rh_lin = C3 * humi_f * humi_f + C2 * humi_f + C1;
joeata2wh 4:2c46c3bc8032 61 rh_true=(((temperature/100)-25)*(T1+T2*humi_f)+rh_lin);
joeata2wh 4:2c46c3bc8032 62 if(rh_true>100)rh_true=100; //cut if the value is outside
joeata2wh 4:2c46c3bc8032 63 if(rh_true<1)rh_true=1; //the physical possible range
joeata2wh 4:2c46c3bc8032 64 humidity = rh_true;
joeata2wh 4:2c46c3bc8032 65 pc.printf("stat=%d Temp: %2.2f RH %2.2f\n\r",stat, temperature, humidity);
joeata2wh 4:2c46c3bc8032 66
joeata2wh 2:dc3e84d595c3 67 wait(3.0);
joeata2wh 0:fa185766e039 68 }
joeata2wh 4:2c46c3bc8032 69 }