SHTxx2013 - SHT V4 5V UART

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frederic blanc / Mbed 2 deprecated SHTxx2013

SHT V4 5V UART

Dependencies: mbed

Fork of SHT_v1 by Stephen McGarry

SHT.cpp@0:df1c8f2961a1, 2010-01-24 (annotated)

Committer:: roselea
Date:: Sun Jan 24 22:00:35 2010 +0000
Revision:: 0:df1c8f2961a1
Child:: 1:0dbbb4802508

Who changed what in which revision?

User	Revision	Line number	New contents of line
roselea	0:df1c8f2961a1	1	/* mbed module to use a Sensirion SHT1x /SHT7x sensor
roselea	0:df1c8f2961a1	2	* Copyright (c) 2007-2009 Stephen McGarry
roselea	0:df1c8f2961a1	3	* Released under the MIT License: http://mbed.org/license/mit
roselea	0:df1c8f2961a1	4	*/
roselea	0:df1c8f2961a1	5
roselea	0:df1c8f2961a1	6	#include "SHT.h"
roselea	0:df1c8f2961a1	7
roselea	0:df1c8f2961a1	8	#include "mbed.h"
roselea	0:df1c8f2961a1	9
roselea	0:df1c8f2961a1	10	SHT::SHT(PinName p_sclk, PinName p_data, SHT_acc p_accuracy) : sclk(p_sclk), data(p_data), accuracy(p_accuracy) {
roselea	0:df1c8f2961a1	11	sclk=0;
roselea	0:df1c8f2961a1	12	data=0; // data pin will be used as open collector pin
roselea	0:df1c8f2961a1	13	data.mode(PullUp); // with the pull up internally active
roselea	0:df1c8f2961a1	14	data.input(); // with line released to go high
roselea	0:df1c8f2961a1	15	temperature = humidity = dewpoint=0.0f;
roselea	0:df1c8f2961a1	16	printf("constructor\n");
roselea	0:df1c8f2961a1	17	}
roselea	0:df1c8f2961a1	18
roselea	0:df1c8f2961a1	19	char SHT::write_byte(byte value)
roselea	0:df1c8f2961a1	20	//----------------------------------------------------------------------------------
roselea	0:df1c8f2961a1	21	// writes a byte on the Sensibus and checks the acknowledge
roselea	0:df1c8f2961a1	22	{
roselea	0:df1c8f2961a1	23	int i;
roselea	0:df1c8f2961a1	24	char error=0;
roselea	0:df1c8f2961a1	25
roselea	0:df1c8f2961a1	26	for (i=0x80;i>0;i/=2) { //shift bit for masking
roselea	0:df1c8f2961a1	27	if (i & value) data.input(); //masking value with i , write to SENSI-BUS
roselea	0:df1c8f2961a1	28	else data.output();
roselea	0:df1c8f2961a1	29	wait_us(1); //ensure sclk is low for min time
roselea	0:df1c8f2961a1	30	sclk=1; //clk for SENSI-BUS
roselea	0:df1c8f2961a1	31	wait_us(1); //pulsewith approx. 2 us
roselea	0:df1c8f2961a1	32	sclk=0;
roselea	0:df1c8f2961a1	33	}
roselea	0:df1c8f2961a1	34	data.input(); //release DATA-line
roselea	0:df1c8f2961a1	35	wait_us(1); //ensure sclk is low for min time
roselea	0:df1c8f2961a1	36	sclk=1; //clk #9 for ack
roselea	0:df1c8f2961a1	37	error=data; //check ack (DATA will be pulled down by SHT11)
roselea	0:df1c8f2961a1	38	wait_us(1);
roselea	0:df1c8f2961a1	39	sclk=0;
roselea	0:df1c8f2961a1	40	return error; //error=1 in case of no acknowledge
roselea	0:df1c8f2961a1	41	}
roselea	0:df1c8f2961a1	42
roselea	0:df1c8f2961a1	43	byte SHT::read_byte(bool send_ack)
roselea	0:df1c8f2961a1	44	//----------------------------------------------------------------------------------
roselea	0:df1c8f2961a1	45	// reads a byte form the Sensibus and gives an acknowledge in case of "ack=1"
roselea	0:df1c8f2961a1	46	{
roselea	0:df1c8f2961a1	47	byte i,val=0;
roselea	0:df1c8f2961a1	48	data.input(); //release DATA-line
roselea	0:df1c8f2961a1	49	for (i=0x80;i>0;i/=2) { //shift bit for masking
roselea	0:df1c8f2961a1	50	wait_us(1);
roselea	0:df1c8f2961a1	51	sclk=1; //clk for SENSI-BUS
roselea	0:df1c8f2961a1	52	if (data) val=(val \| i); //read bit
roselea	0:df1c8f2961a1	53	wait_us(1);
roselea	0:df1c8f2961a1	54	sclk=0;
roselea	0:df1c8f2961a1	55	}
roselea	0:df1c8f2961a1	56	wait_us(1);
roselea	0:df1c8f2961a1	57	if (send_ack) data.output(); // if ack needed then drive data low
roselea	0:df1c8f2961a1	58	sclk=1; //clk #9 for ack
roselea	0:df1c8f2961a1	59	wait_us(1);
roselea	0:df1c8f2961a1	60	sclk=0;
roselea	0:df1c8f2961a1	61	data.input(); //release DATA-line
roselea	0:df1c8f2961a1	62	return val;
roselea	0:df1c8f2961a1	63	}
roselea	0:df1c8f2961a1	64
roselea	0:df1c8f2961a1	65	void SHT::trans_start(void)
roselea	0:df1c8f2961a1	66	//----------------------------------------------------------------------------------
roselea	0:df1c8f2961a1	67	// generates a transmission start
roselea	0:df1c8f2961a1	68	// _____ ________
roselea	0:df1c8f2961a1	69	// DATA: \|_______\|
roselea	0:df1c8f2961a1	70	// ___ ___
roselea	0:df1c8f2961a1	71	// SCK : ___\| \|___\| \|______
roselea	0:df1c8f2961a1	72	{
roselea	0:df1c8f2961a1	73	data.input();
roselea	0:df1c8f2961a1	74	sclk=0; //Initial state
roselea	0:df1c8f2961a1	75	wait_us(1);
roselea	0:df1c8f2961a1	76	sclk=1;
roselea	0:df1c8f2961a1	77	wait_us(1);
roselea	0:df1c8f2961a1	78	data.output(); // data low
roselea	0:df1c8f2961a1	79	wait_us(1);
roselea	0:df1c8f2961a1	80	sclk=0;
roselea	0:df1c8f2961a1	81	wait_us(1);
roselea	0:df1c8f2961a1	82	sclk=1;
roselea	0:df1c8f2961a1	83	wait_us(1);
roselea	0:df1c8f2961a1	84	data.input(); // allow data to high
roselea	0:df1c8f2961a1	85	wait_us(1);
roselea	0:df1c8f2961a1	86	sclk=0;
roselea	0:df1c8f2961a1	87	wait_us(1);
roselea	0:df1c8f2961a1	88	}
roselea	0:df1c8f2961a1	89
roselea	0:df1c8f2961a1	90	void SHT::connection_reset(void)
roselea	0:df1c8f2961a1	91	//----------------------------------------------------------------------------------
roselea	0:df1c8f2961a1	92	// communication reset: DATA-line=1 and at least 9 SCK cycles followed by transstart
roselea	0:df1c8f2961a1	93	// _____________________________________________________ ________
roselea	0:df1c8f2961a1	94	// DATA: \|_______\|
roselea	0:df1c8f2961a1	95	// _ _ _ _ _ _ _ _ _ ___ ___
roselea	0:df1c8f2961a1	96	// SCK : __\| \|__\| \|__\| \|__\| \|__\| \|__\| \|__\| \|__\| \|__\| \|______\| \|___\| \|______
roselea	0:df1c8f2961a1	97	{
roselea	0:df1c8f2961a1	98	int i;
roselea	0:df1c8f2961a1	99	data.input(); // allow data high
roselea	0:df1c8f2961a1	100	sclk=0; // and clk low
roselea	0:df1c8f2961a1	101	for (i=0;i<9;i++) { // 9 SCK cycles
roselea	0:df1c8f2961a1	102	wait_us(1);
roselea	0:df1c8f2961a1	103	sclk=1;
roselea	0:df1c8f2961a1	104	wait_us(1);
roselea	0:df1c8f2961a1	105	sclk=0;
roselea	0:df1c8f2961a1	106	}
roselea	0:df1c8f2961a1	107	}
roselea	0:df1c8f2961a1	108	char SHT::soft_reset(void)
roselea	0:df1c8f2961a1	109	//----------------------------------------------------------------------------------
roselea	0:df1c8f2961a1	110	// resets the sensor by a softreset
roselea	0:df1c8f2961a1	111	{
roselea	0:df1c8f2961a1	112	char error=0;
roselea	0:df1c8f2961a1	113	SHT::connection_reset(); //reset communication
roselea	0:df1c8f2961a1	114	trans_start();
roselea	0:df1c8f2961a1	115	error+=write_byte(com_reset); //send RESET-command to sensor
roselea	0:df1c8f2961a1	116	return error; //error=1 in case of no response form the sensor
roselea	0:df1c8f2961a1	117	}
roselea	0:df1c8f2961a1	118
roselea	0:df1c8f2961a1	119	char SHT::read_status(byte &value)
roselea	0:df1c8f2961a1	120	//----------------------------------------------------------------------------------
roselea	0:df1c8f2961a1	121	// reads the status register with checksum (8-bit)
roselea	0:df1c8f2961a1	122	{
roselea	0:df1c8f2961a1	123	//byte checksum;
roselea	0:df1c8f2961a1	124
roselea	0:df1c8f2961a1	125	char error=0;
roselea	0:df1c8f2961a1	126	trans_start(); //transmission start
roselea	0:df1c8f2961a1	127	error=write_byte(com_read_status_reg); //send command to sensor
roselea	0:df1c8f2961a1	128	value=read_byte(send_ack); //read status register (8-bit)
roselea	0:df1c8f2961a1	129	/* checksum= */
roselea	0:df1c8f2961a1	130	(void)read_byte(no_ack); //read checksum (8-bit)
roselea	0:df1c8f2961a1	131	// check the checksum ??
roselea	0:df1c8f2961a1	132	return error; //error=1 in case of no response form the sensor
roselea	0:df1c8f2961a1	133	}
roselea	0:df1c8f2961a1	134
roselea	0:df1c8f2961a1	135	char SHT::write_status(byte value)
roselea	0:df1c8f2961a1	136	//----------------------------------------------------------------------------------
roselea	0:df1c8f2961a1	137	// writes the status register (8-bit)
roselea	0:df1c8f2961a1	138	{
roselea	0:df1c8f2961a1	139	char error=0;
roselea	0:df1c8f2961a1	140	trans_start(); //transmission start
roselea	0:df1c8f2961a1	141	error+=write_byte(com_write_status_reg); //send command to sensor
roselea	0:df1c8f2961a1	142	error+=write_byte(value); //send value of status register
roselea	0:df1c8f2961a1	143	return error; //error>=1 in case of no response form the sensor
roselea	0:df1c8f2961a1	144	}
roselea	0:df1c8f2961a1	145
roselea	0:df1c8f2961a1	146	char SHT::measure(int &value, byte command)
roselea	0:df1c8f2961a1	147	//----------------------------------------------------------------------------------
roselea	0:df1c8f2961a1	148	// makes a measurement (humidity/temperature) with checksum
roselea	0:df1c8f2961a1	149	{
roselea	0:df1c8f2961a1	150	unsigned int i;
roselea	0:df1c8f2961a1	151	byte msb;
roselea	0:df1c8f2961a1	152	// byte checksum;
roselea	0:df1c8f2961a1	153
roselea	0:df1c8f2961a1	154	trans_start(); //transmission start
roselea	0:df1c8f2961a1	155	if (write_byte(command)) return 1; // if command fails return
roselea	0:df1c8f2961a1	156
roselea	0:df1c8f2961a1	157	for (i=10000;i;i--) { //wait until sensor has finished the measurement
roselea	0:df1c8f2961a1	158	wait_us(100);
roselea	0:df1c8f2961a1	159	if (data==0) break;
roselea	0:df1c8f2961a1	160	}
roselea	0:df1c8f2961a1	161	if (data) return 1; // or timeout (~1 sec.) is reached !!
roselea	0:df1c8f2961a1	162	msb = read_byte(send_ack); //read the first byte (MSB)
roselea	0:df1c8f2961a1	163	value = msb*256 + read_byte(send_ack); //read the second byte (LSB)
roselea	0:df1c8f2961a1	164	/* checksum= */
roselea	0:df1c8f2961a1	165	(void)read_byte(no_ack); //read checksum
roselea	0:df1c8f2961a1	166	return 0;
roselea	0:df1c8f2961a1	167	}
roselea	0:df1c8f2961a1	168
roselea	0:df1c8f2961a1	169	void SHT::calculate()
roselea	0:df1c8f2961a1	170	//----------------------------------------------------------------------------------------
roselea	0:df1c8f2961a1	171	// calculates temperature [°C] and humidity [%RH]
roselea	0:df1c8f2961a1	172	// input : hum [Ticks] (12 bit)
roselea	0:df1c8f2961a1	173	// temp [Ticks] (14 bit)
roselea	0:df1c8f2961a1	174	// output: humidity [%RH]
roselea	0:df1c8f2961a1	175	// temperature [°C]
roselea	0:df1c8f2961a1	176	{
roselea	0:df1c8f2961a1	177	const float C1=-4.0; // for 12 Bit
roselea	0:df1c8f2961a1	178	const float C2=+0.0405; // for 12 Bit
roselea	0:df1c8f2961a1	179	const float C3=-0.0000028; // for 12 Bit
roselea	0:df1c8f2961a1	180	//const float T1=+0.01; // for 14 Bit @ 5V
roselea	0:df1c8f2961a1	181	//const float T2=+0.00008; // for 14 Bit @ 5V
roselea	0:df1c8f2961a1	182
roselea	0:df1c8f2961a1	183	float rh; // rh: Humidity [Ticks] 12 Bit
roselea	0:df1c8f2961a1	184	float t; // t: Temperature [Ticks] 14 Bit
roselea	0:df1c8f2961a1	185	//float rh_lin; // rh_lin: Humidity linear
roselea	0:df1c8f2961a1	186	if (accuracy==SHT_low) {
roselea	0:df1c8f2961a1	187	rh=hum*16; // rescale to high accuracy values - 8 to 12 bits
roselea	0:df1c8f2961a1	188	t=temp*4; // and 12 to 14 bits
roselea	0:df1c8f2961a1	189	} else {
roselea	0:df1c8f2961a1	190	rh=hum;
roselea	0:df1c8f2961a1	191	t=temp;
roselea	0:df1c8f2961a1	192	}
roselea	0:df1c8f2961a1	193
roselea	0:df1c8f2961a1	194	temperature=t*0.01 - 40; //calc. temperature from ticks to [°C]
roselea	0:df1c8f2961a1	195	humidity=C3rhrh + C2*rh + C1; //calc. humidity from ticks to [%RH]
roselea	0:df1c8f2961a1	196	// =(temperature-25)(T1+T2rh)+rh_lin; //calc. temperature compensated humidity [%RH] (ignore as never >0.25%)
roselea	0:df1c8f2961a1	197	if (humidity>100)humidity=100; //cut if the value is outside of
roselea	0:df1c8f2961a1	198	if (humidity<0.1)humidity=0.1; //the physical possible range
roselea	0:df1c8f2961a1	199	}
roselea	0:df1c8f2961a1	200
roselea	0:df1c8f2961a1	201	float SHT::get_temperature() { // get the most recent temp reading
roselea	0:df1c8f2961a1	202	return temperature;
roselea	0:df1c8f2961a1	203	}
roselea	0:df1c8f2961a1	204
roselea	0:df1c8f2961a1	205	float SHT::get_humidity() { // get the most recent humidity reading
roselea	0:df1c8f2961a1	206	return humidity;
roselea	0:df1c8f2961a1	207	}
roselea	0:df1c8f2961a1	208
roselea	0:df1c8f2961a1	209	float SHT::get_dewpoint() { // get the most recent dewpoint value
roselea	0:df1c8f2961a1	210	return dewpoint;
roselea	0:df1c8f2961a1	211	}
roselea	0:df1c8f2961a1	212
roselea	0:df1c8f2961a1	213	void SHT::update(SHT_acc acc) { // update stored values from sensor
roselea	0:df1c8f2961a1	214	int error=0;
roselea	0:df1c8f2961a1	215	connection_reset();
roselea	0:df1c8f2961a1	216	if (acc!=accuracy) {
roselea	0:df1c8f2961a1	217	accuracy=acc;
roselea	0:df1c8f2961a1	218	error+=write_status((acc==SHT_low)?0x01:0x00); //set the status reg to high or low accuarcy
roselea	0:df1c8f2961a1	219	}
roselea	0:df1c8f2961a1	220	error+=measure(temp,com_measure_temp);
roselea	0:df1c8f2961a1	221	error+=measure(hum,com_measure_humid);
roselea	0:df1c8f2961a1	222	if (!error) calculate();
roselea	0:df1c8f2961a1	223
roselea	0:df1c8f2961a1	224	}

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Type:	Program
Mbed OS support:	Mbed 2 deprecated
Created:	23 Feb 2016
Imports:	3
Forks:	0
Commits:	2
Dependents:	0
Dependencies:	1
Followers:	2

SHT.cpp@0:df1c8f2961a1, 2010-01-24 (annotated)

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