La Suno / Mbed 2 deprecated afero_poc15_180216

Gas Pressure Display Updated Power control for Pressure sensor added

Dependencies:   UniGraphic mbed vt100

sensors/PSE530.cpp@0:37c8ecde13c2, 2018-02-16 (annotated)

Committer:
Rhyme
Date:
Fri Feb 16 08:27:50 2018 +0000
Revision:
0:37c8ecde13c2
control PSE530 power via PTC5 (pse530_en)

Who changed what in which revision?

UserRevisionLine numberNew contents of line
Rhyme 0:37c8ecde13c2 1 #include "mbed.h"
Rhyme 0:37c8ecde13c2 2 #include "PSE530.h"
Rhyme 0:37c8ecde13c2 3
Rhyme 0:37c8ecde13c2 4 /**
Rhyme 0:37c8ecde13c2 5 * SMC PSE530 pressure sensor
Rhyme 0:37c8ecde13c2 6 * analog output 1.0V - 5.0V
Rhyme 0:37c8ecde13c2 7 * 1.0V : 0
Rhyme 0:37c8ecde13c2 8 * 5.0V : 1MPa
Rhyme 0:37c8ecde13c2 9 * (at 0.6V : -0.1MPa)
Rhyme 0:37c8ecde13c2 10 * Our sensor I/F converts 0-5V to 0-3V
Rhyme 0:37c8ecde13c2 11 * So we suppose V = Analog Float Value : Pressure
Rhyme 0:37c8ecde13c2 12 * 0.6V = 0.2 : 0
Rhyme 0:37c8ecde13c2 13 * 3.0V = 1.0 : 1MPa
Rhyme 0:37c8ecde13c2 14 */
Rhyme 0:37c8ecde13c2 15
Rhyme 0:37c8ecde13c2 16 /**
Rhyme 0:37c8ecde13c2 17 * conversion from Pa to kgf/cm2
Rhyme 0:37c8ecde13c2 18 * 98,066.5 Pa = 1 kgf/cm2
Rhyme 0:37c8ecde13c2 19 * 1 Pa = 1 / 98066.6 kgf/cm2
Rhyme 0:37c8ecde13c2 20 */
Rhyme 0:37c8ecde13c2 21
Rhyme 0:37c8ecde13c2 22 PSE530::PSE530(AnalogIn *ain)
Rhyme 0:37c8ecde13c2 23 {
Rhyme 0:37c8ecde13c2 24 _ain = ain ;
Rhyme 0:37c8ecde13c2 25 }
Rhyme 0:37c8ecde13c2 26
Rhyme 0:37c8ecde13c2 27 PSE530::~PSE530(void)
Rhyme 0:37c8ecde13c2 28 {
Rhyme 0:37c8ecde13c2 29 if (_ain) {
Rhyme 0:37c8ecde13c2 30 delete _ain ;
Rhyme 0:37c8ecde13c2 31 }
Rhyme 0:37c8ecde13c2 32 }
Rhyme 0:37c8ecde13c2 33
Rhyme 0:37c8ecde13c2 34 /**
Rhyme 0:37c8ecde13c2 35 * On FRDM-KL25Z ADC's AREF is about 3.28V
Rhyme 0:37c8ecde13c2 36 * Where the converted pressure output is 0 to 3.21V
Rhyme 0:37c8ecde13c2 37 * So we must map ADC output 0 to 3.21/3.28 as full scale
Rhyme 0:37c8ecde13c2 38 *
Rhyme 0:37c8ecde13c2 39 * Then according to the datasheet of PSE530
Rhyme 0:37c8ecde13c2 40 * when full range is 0V to 5V
Rhyme 0:37c8ecde13c2 41 * 1V is 0 and 5V is 1MPa which is converted to
Rhyme 0:37c8ecde13c2 42 * 0.642/3.28 to 3.21/3.28 ~ 0.195731 to 0.9786585.
Rhyme 0:37c8ecde13c2 43 * The linear equation of
Rhyme 0:37c8ecde13c2 44 * y = a x + b
Rhyme 0:37c8ecde13c2 45 * 0 = a * 0.195731 + b
Rhyme 0:37c8ecde13c2 46 * 1 = a * 0.978658 + b
Rhyme 0:37c8ecde13c2 47 * results a = 1.277, b = -0.250
Rhyme 0:37c8ecde13c2 48 */
Rhyme 0:37c8ecde13c2 49 float PSE530::getPressure(void)
Rhyme 0:37c8ecde13c2 50 {
Rhyme 0:37c8ecde13c2 51 float coef_A = 1.277 ;
Rhyme 0:37c8ecde13c2 52 float coef_B = -0.250 ;
Rhyme 0:37c8ecde13c2 53 float av = 0.0 ;
Rhyme 0:37c8ecde13c2 54 float value = 0.0 ;
Rhyme 0:37c8ecde13c2 55 av = coef_A * _ain->read() + coef_B ;
Rhyme 0:37c8ecde13c2 56 // printf("Pressure ADC = %.4f\n", av) ;
Rhyme 0:37c8ecde13c2 57 value = 1000000 * av ; /* 1MPa at 1.0 */
Rhyme 0:37c8ecde13c2 58 value = value / 98066.5 ; /* Pa -> kgf/cm2 */
Rhyme 0:37c8ecde13c2 59 return( value ) ;
Rhyme 0:37c8ecde13c2 60 }