hsc - | Mbed

Users » gbeardall » Code » hsc

main.cpp@1:d01abb5e6f52, 2011-10-17 (annotated)

Committer:: gbeardall
Date:: Mon Oct 17 10:41:37 2011 +0000
Revision:: 1:d01abb5e6f52
Parent:: 0:2fdc6095d7b4

Who changed what in which revision?

User	Revision	Line number	New contents of line
gbeardall	1:d01abb5e6f52	1	/*
gbeardall	1:d01abb5e6f52	2	* Honeywell Pressure Sensor
gbeardall	1:d01abb5e6f52	3	*
gbeardall	1:d01abb5e6f52	4	*/
gbeardall	1:d01abb5e6f52	5
gbeardall	1:d01abb5e6f52	6	#include <math.h>
gbeardall	1:d01abb5e6f52	7
gbeardall	0:2fdc6095d7b4	8	#include "mbed.h"
gbeardall	0:2fdc6095d7b4	9
gbeardall	0:2fdc6095d7b4	10	DigitalOut myled(LED1);
gbeardall	0:2fdc6095d7b4	11
gbeardall	0:2fdc6095d7b4	12	// http://sensing.honeywell.com/index.cfm/ci_id/157750/la_id/1/document/1/re_id/0
gbeardall	0:2fdc6095d7b4	13	// http://sensing.honeywell.com/index.cfm/ci_id/156988/la_id/1/document/1/re_id/0
gbeardall	0:2fdc6095d7b4	14
gbeardall	0:2fdc6095d7b4	15	#define HSC_2A 0x28
gbeardall	0:2fdc6095d7b4	16
gbeardall	0:2fdc6095d7b4	17	int main() {
gbeardall	0:2fdc6095d7b4	18
gbeardall	0:2fdc6095d7b4	19	// BMP085 bmp085(p28, p27); //bmp085(p9, p10); // sda, scl
gbeardall	0:2fdc6095d7b4	20
gbeardall	0:2fdc6095d7b4	21	printf("\rhsc\n\r");
gbeardall	0:2fdc6095d7b4	22
gbeardall	0:2fdc6095d7b4	23	I2C i2c(p28, p27);
gbeardall	0:2fdc6095d7b4	24
gbeardall	0:2fdc6095d7b4	25	int id = HSC_2A;
gbeardall	0:2fdc6095d7b4	26
gbeardall	0:2fdc6095d7b4	27	i2c.frequency(100000); // 100k - 400k
gbeardall	0:2fdc6095d7b4	28
gbeardall	0:2fdc6095d7b4	29	while(1) {
gbeardall	0:2fdc6095d7b4	30
gbeardall	0:2fdc6095d7b4	31	#if 0
gbeardall	0:2fdc6095d7b4	32	i2c.start();
gbeardall	0:2fdc6095d7b4	33	i2c.write((id<<1) \| 1);
gbeardall	0:2fdc6095d7b4	34	int b1 = i2c.read(1);
gbeardall	0:2fdc6095d7b4	35	int b2 = i2c.read(1);
gbeardall	0:2fdc6095d7b4	36	int t1 = i2c.read(1);
gbeardall	0:2fdc6095d7b4	37	int t2 = i2c.read(0);
gbeardall	0:2fdc6095d7b4	38	i2c.stop();
gbeardall	0:2fdc6095d7b4	39	printf("%02X %02X %02X %02X\n\r", b1, b2, t1, t2);
gbeardall	0:2fdc6095d7b4	40	#else
gbeardall	0:2fdc6095d7b4	41	unsigned char data[4];
gbeardall	0:2fdc6095d7b4	42	i2c.read((id<<1)\|1, (char*)data, sizeof(data));
gbeardall	0:2fdc6095d7b4	43	//printf("%02X %02X %02X %02X\n\r", data[0], data[1], data[2], data[3]);
gbeardall	1:d01abb5e6f52	44
gbeardall	0:2fdc6095d7b4	45	int st = data[0]>>6; // status
gbeardall	0:2fdc6095d7b4	46	int bd = ((data[0] & 0x3f) << 8) \| data[1]; // bridge data
gbeardall	0:2fdc6095d7b4	47	int td = ((data[2]<<8) \| data[3]) >> 5; // temp data
gbeardall	0:2fdc6095d7b4	48
gbeardall	1:d01abb5e6f52	49	// P: 14 bits
gbeardall	1:d01abb5e6f52	50	// Cmin=2^14-1.1 Cmax=2^14-1.9
gbeardall	1:d01abb5e6f52	51	// Pmin=0 Pmax=15
gbeardall	1:d01abb5e6f52	52	float p = (((float)bd-1638)*(15-0)/(14745-1638))+0; // convert raw data to psi
gbeardall	1:d01abb5e6f52	53	p = p * 68.9475729; // convert psi to hPa
gbeardall	0:2fdc6095d7b4	54
gbeardall	1:d01abb5e6f52	55	// T: 11 bits (Cmax=2047=2^11-1)
gbeardall	1:d01abb5e6f52	56	float t = (((float)td*200)/2047)-50; // convert raw data to deg C
gbeardall	0:2fdc6095d7b4	57	printf("%d: %.2f hPa %.2f C\n\r", st, p, t);
gbeardall	0:2fdc6095d7b4	58
gbeardall	0:2fdc6095d7b4	59	wait(1);
gbeardall	0:2fdc6095d7b4	60	#endif
gbeardall	0:2fdc6095d7b4	61
gbeardall	0:2fdc6095d7b4	62	myled = 1;
gbeardall	0:2fdc6095d7b4	63	wait(0.2);
gbeardall	0:2fdc6095d7b4	64	myled = 0;
gbeardall	0:2fdc6095d7b4	65	wait(0.2);
gbeardall	0:2fdc6095d7b4	66
gbeardall	0:2fdc6095d7b4	67	} // while
gbeardall	0:2fdc6095d7b4	68
gbeardall	0:2fdc6095d7b4	69	} // main
gbeardall	1:d01abb5e6f52	70
gbeardall	1:d01abb5e6f52	71
gbeardall	1:d01abb5e6f52	72	// http://en.wikipedia.org/wiki/Barometric_formula
gbeardall	1:d01abb5e6f52	73	const float layers[][4] = {
gbeardall	1:d01abb5e6f52	74	// Height[m], Pressure[Pa], Temp[K], Lapse[K/m], Subscript
gbeardall	1:d01abb5e6f52	75	0, 101325.0, 288.15, -0.0065, // 0
gbeardall	1:d01abb5e6f52	76	11000, 22632.1, 216.65, 0.0, // 1
gbeardall	1:d01abb5e6f52	77	20000, 5474.89, 216.65, 0.001, // 2
gbeardall	1:d01abb5e6f52	78	32000, 868.019, 228.65, 0.0028, // 3
gbeardall	1:d01abb5e6f52	79	47000, 110.906, 270.65, 0.0, // 4
gbeardall	1:d01abb5e6f52	80	51000, 66.9389, 270.65, -0.0028, // 5
gbeardall	1:d01abb5e6f52	81	71000, 3.95642, 214.65, -0.002 // 6
gbeardall	1:d01abb5e6f52	82	};
gbeardall	1:d01abb5e6f52	83
gbeardall	1:d01abb5e6f52	84	enum { L_HEIGHT=0, L_PRESS, L_TEMP, L_LAPSE };
gbeardall	1:d01abb5e6f52	85
gbeardall	1:d01abb5e6f52	86	const float g = 9.80665;
gbeardall	1:d01abb5e6f52	87	const float M = 0.0289644;
gbeardall	1:d01abb5e6f52	88	const float R = 8.31432;
gbeardall	1:d01abb5e6f52	89	const float Ta = -273.15; // Absolute zero [deg C]
gbeardall	1:d01abb5e6f52	90
gbeardall	1:d01abb5e6f52	91	// Search for subscript which matches pressure range
gbeardall	1:d01abb5e6f52	92	// Choose appropriate formula and plug in values
gbeardall	1:d01abb5e6f52	93	// Lookup derived h in table and check subscript is still same, otherwise recalculate
gbeardall	1:d01abb5e6f52	94	// Add height correction
gbeardall	1:d01abb5e6f52	95
gbeardall	1:d01abb5e6f52	96	// Pass in pressure and temperature from sensor
gbeardall	1:d01abb5e6f52	97	// Return height[m]
gbeardall	1:d01abb5e6f52	98	float pressureToHeight(float p, float t) {
gbeardall	1:d01abb5e6f52	99	float h = -999; // error
gbeardall	1:d01abb5e6f52	100	int b;
gbeardall	1:d01abb5e6f52	101	int tries;
gbeardall	1:d01abb5e6f52	102
gbeardall	1:d01abb5e6f52	103	// Search backwards thru layers for our pressure
gbeardall	1:d01abb5e6f52	104	for(b = 6; b >= 0; --b) {
gbeardall	1:d01abb5e6f52	105	if(p <= layers[b][1]) break;
gbeardall	1:d01abb5e6f52	106	}
gbeardall	1:d01abb5e6f52	107	if(b < 0) b = 0; // adjust so can have -ve heights
gbeardall	1:d01abb5e6f52	108	int b1 = b;
gbeardall	1:d01abb5e6f52	109
gbeardall	1:d01abb5e6f52	110	// Only retry limited times
gbeardall	1:d01abb5e6f52	111	for(tries = 10; tries; --tries) {
gbeardall	1:d01abb5e6f52	112
gbeardall	1:d01abb5e6f52	113	float Hb = layers[b][0];
gbeardall	1:d01abb5e6f52	114	float Pb = layers[b][1];
gbeardall	1:d01abb5e6f52	115	float Tb = layers[b][2]; //??? Tb = t - Ta;
gbeardall	1:d01abb5e6f52	116	float Lb = layers[b][3];
gbeardall	1:d01abb5e6f52	117
gbeardall	1:d01abb5e6f52	118	if(Lb != 0.0)
gbeardall	1:d01abb5e6f52	119	//h = (log(gM/R/Lb)/log(p/Pb)Tb - Tb)/Lb + Hb; // Equation 1 (non-zero lapse rate)
gbeardall	1:d01abb5e6f52	120	h = (Tb/exp(RLb/g/Mlog(p/Pb))-Tb)/Lb + Hb;
gbeardall	1:d01abb5e6f52	121	else
gbeardall	1:d01abb5e6f52	122	h = -log(p/Pb)RTb/g/M + Hb; // Equation 2 (zero lapse rate)
gbeardall	1:d01abb5e6f52	123
gbeardall	1:d01abb5e6f52	124	// Search again for derived height
gbeardall	1:d01abb5e6f52	125	for(b = 6; b >= 0; --b) {
gbeardall	1:d01abb5e6f52	126	if(h <= layers[b][0]) break;
gbeardall	1:d01abb5e6f52	127	}
gbeardall	1:d01abb5e6f52	128
gbeardall	1:d01abb5e6f52	129	if(b == b1) break; // gave same subscript, so we can stop
gbeardall	1:d01abb5e6f52	130	b1 = b;
gbeardall	1:d01abb5e6f52	131
gbeardall	1:d01abb5e6f52	132	} // for - tries
gbeardall	1:d01abb5e6f52	133
gbeardall	1:d01abb5e6f52	134	if(tries <= 0) h = -999; // error
gbeardall	1:d01abb5e6f52	135
gbeardall	1:d01abb5e6f52	136
gbeardall	1:d01abb5e6f52	137	return h;
gbeardall	1:d01abb5e6f52	138
gbeardall	1:d01abb5e6f52	139	} // pressureToHeight
gbeardall	1:d01abb5e6f52	140
gbeardall	1:d01abb5e6f52	141	/end/
gbeardall	1:d01abb5e6f52	142

Repository toolbox

Export to desktop IDE

Build repository

Repository details

Type:	Program
Mbed OS support:	Mbed 2 deprecated
Created:	07 Sep 2011
Imports:	12
Forks:	0
Commits:	2
Dependents:	0
Dependencies:	1
Followers:	1

main.cpp@1:d01abb5e6f52, 2011-10-17 (annotated)

Who changed what in which revision?

Repository toolbox

Repository details

Important Information for this Arm website

Access Warning