Skip to content

Commit

Permalink
Merge pull request #6 from hallard/master
Browse files Browse the repository at this point in the history 
Added SI7021 I2C Temperature Humidity Sensor
  • Loading branch information
@martinusGH
martinusGH committed Oct 12, 2015
2 parents 40337b9 + 6223fb2 commit d1c53e7
Show file tree
Hide file tree
Showing 3 changed files with 379 additions and 2 deletions.
5 changes: 4 additions & 1 deletion WebServer.ino
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1080,6 +1080,9 @@ void handle_i2cscanner() {
case 0x23:
reply += F("BH1750 Lux Sensor");
break;
case 0x40:
reply += F("SI7021 Temp/Hum Sensor");
break;
case 0x48:
reply += F("PCF8591 ADC");
break;
Expand Down Expand Up @@ -1776,4 +1779,4 @@ void handleFileUpload()
}
}
#endif


371 changes: 371 additions & 0 deletions _P014_SI7021.ino
View file
Original file line number Diff line number Diff line change
@@ -0,0 +1,371 @@
//#######################################################################################################
//######################## Plugin 014 SI7021 I2C Temperature Humidity Sensor ###########################
//#######################################################################################################
// 12-10-2015 Charles-Henri Hallard, see my projects and blog at https://hallard.me

#define PLUGIN_014
#define PLUGIN_ID_014 14
#define PLUGIN_NAME_014 "Temp + Hum SI7021"
#define PLUGIN_VALUENAME1_014 "Temperature"
#define PLUGIN_VALUENAME2_014 "Humidity"

boolean Plugin_014_init = false;

// ======================================
// SI7021 sensor
// ======================================
#define SI7021_I2C_ADDRESS 0x40 // I2C address for the sensor
#define SI7021_MEASURE_TEMP0 0xE0 // Can be read only after a RH conversion done
#define SI7021_MEASURE_TEMP 0xE3 // Default hold
#define SI7021_MEASURE_HUM 0xE5 // Default hold
#define SI7021_MEASURE_NOHOLD 0x80 // NO HOLD Bit flag
#define SI7021_WRITE_REG 0xE6
#define SI7021_READ_REG 0xE7
#define SI7021_SOFT_RESET 0xFE

// SI7021 Sensor resolution
// default at power up is SI7021_RESOLUTION_14T_12RH
#define SI7021_RESOLUTION_14T_12RH 0x00 // 12 bits RH / 14 bits Temp
#define SI7021_RESOLUTION_13T_10RH 0x80 // 10 bits RH / 13 bits Temp
#define SI7021_RESOLUTION_12T_08RH 0x01 // 8 bits RH / 12 bits Temp
#define SI7021_RESOLUTION_11T_11RH 0x81 // 11 bits RH / 11 bits Temp
#define SI7021_RESOLUTION_MASK 0B01111110

uint8_t si7021_humidity; // latest humidity value read
int16_t si7021_temperature; // latest temperature value read (*100)

boolean Plugin_014(byte function, struct EventStruct *event, String& string)
{
boolean success = false;

switch (function)
{
case PLUGIN_DEVICE_ADD:
{
Device[++deviceCount].Number = PLUGIN_ID_014;
Device[deviceCount].Type = DEVICE_TYPE_I2C;
Device[deviceCount].VType = SENSOR_TYPE_TEMP_HUM;
Device[deviceCount].Ports = 0;
Device[deviceCount].PullUpOption = false;
Device[deviceCount].InverseLogicOption = false;
Device[deviceCount].FormulaOption = true;
Device[deviceCount].ValueCount = 2;
break;
}

case PLUGIN_GET_DEVICENAME:
{
string = F(PLUGIN_NAME_014);
break;
}

case PLUGIN_GET_DEVICEVALUENAMES:
{
strcpy_P(ExtraTaskSettings.TaskDeviceValueNames[0], PSTR(PLUGIN_VALUENAME1_014));
strcpy_P(ExtraTaskSettings.TaskDeviceValueNames[1], PSTR(PLUGIN_VALUENAME2_014));
break;
}

case PLUGIN_WEBFORM_LOAD:
{
#define SI7021_RESOLUTION_OPTION 4

byte choice = Settings.TaskDevicePluginConfig[event->TaskIndex][0];
String options[SI7021_RESOLUTION_OPTION];
int optionValues[SI7021_RESOLUTION_OPTION];
optionValues[0] = SI7021_RESOLUTION_14T_12RH;
options[0] = F("Temp 14 bits / RH 12 bits");
optionValues[1] = SI7021_RESOLUTION_13T_10RH;
options[1] = F("Temp 13 bits / RH 10 bits");
optionValues[2] = SI7021_RESOLUTION_12T_08RH;
options[2] = F("Temp 12 bits / RH 8 bits");
optionValues[3] = SI7021_RESOLUTION_11T_11RH;
options[3] = F("Temp 11 bits / RH 11 bits");

string += F("<TR><TD>Resolution (bits):<TD><select name='plugin_014_res'>");
for (byte x = 0; x < SI7021_RESOLUTION_OPTION; x++)
{
string += F("<option value='");
string += optionValues[x];
string += "'";
if (choice == optionValues[x])
string += F(" selected");
string += ">";
string += options[x];
string += F("</option>");
}
string += F("</select>");

success = true;
break;
}

case PLUGIN_WEBFORM_SAVE:
{
String plugin1 = WebServer.arg("plugin_014_res");
Settings.TaskDevicePluginConfig[event->TaskIndex][0] = plugin1.toInt();
Plugin_014_init = false; // Force device setup next time
success = true;
break;
}

case PLUGIN_READ:
{
// Get sensor resolution configuration
uint8_t res = Settings.TaskDevicePluginConfig[event->TaskIndex][0];

if (!Plugin_014_init) {
Plugin_014_init = Plugin_014_si7021_begin(res);
}

// Read values
if (Plugin_014_si7021_readValues(res) == 0) {
UserVar[event->BaseVarIndex] = si7021_temperature/100.0;
UserVar[event->BaseVarIndex + 1] = si7021_humidity;
success = true;
/*
String log = F("SI7021 : Temperature: ");
log += UserVar[event->BaseVarIndex];
addLog(LOG_LEVEL_INFO,log);
log = F("SI7021 : Humidity: ");
log += UserVar[event->BaseVarIndex + 1];
addLog(LOG_LEVEL_INFO,log);
*/
} else {
String log = F("SI7021 : Read Error!");
addLog(LOG_LEVEL_INFO,log);
}

break;
}

}
return success;
}

/* ======================================================================
Function: Plugin_014_si7021_begin
Purpose : read the user register from the sensor
Input : user register value filled by function
Output : true if okay
Comments: -
====================================================================== */
boolean Plugin_014_si7021_begin(uint8_t resolution)
{
uint8_t ret;

// Set the resolution we want
ret = Plugin_014_si7021_setResolution(resolution);
if ( ret == 0 ) {
ret = true;
} else {
String log = F("SI7021 : Res=0x");
log += String(resolution,HEX);
log += F(" => Error 0x");
log += String(ret,HEX);
addLog(LOG_LEVEL_INFO,log);
ret = false;
}

return ret;
}

/* ======================================================================
Function: Plugin_014_si7021_checkCRC
Purpose : check the CRC of received data
Input : value read from sensor
Output : CRC read from sensor
Comments: 0 if okay
====================================================================== */
uint8_t Plugin_014_si7021_checkCRC(uint16_t data, uint8_t check)
{
uint32_t remainder, divisor;

//Pad with 8 bits because we have to add in the check value
remainder = (uint32_t)data << 8;

// From: http://www.nongnu.org/avr-libc/user-manual/group__util__crc.html
// POLYNOMIAL = 0x0131 = x^8 + x^5 + x^4 + 1 : http://en.wikipedia.org/wiki/Computation_of_cyclic_redundancy_checks
// 0x988000 is the 0x0131 polynomial shifted to farthest left of three bytes
divisor = (uint32_t) 0x988000;

// Add the check value
remainder |= check;

// Operate on only 16 positions of max 24.
// The remaining 8 are our remainder and should be zero when we're done.
for (uint8_t i = 0 ; i < 16 ; i++) {
//Check if there is a one in the left position
if( remainder & (uint32_t)1<<(23 - i) )
remainder ^= divisor;

//Rotate the divisor max 16 times so that we have 8 bits left of a remainder
divisor >>= 1;
}
return ((uint8_t) remainder);
}

/* ======================================================================
Function: si7021_readRegister
Purpose : read the user register from the sensor
Input : user register value filled by function
Output : 0 if okay
Comments: -
====================================================================== */
int8_t Plugin_014_si7021_readRegister(uint8_t * value)
{
uint8_t error ;

// Request user register
Wire.beginTransmission(SI7021_I2C_ADDRESS);
Wire.write(SI7021_READ_REG);
Wire.endTransmission();

// request 1 byte result
Wire.requestFrom(SI7021_I2C_ADDRESS, 1);
if (Wire.available()>=1) {
*value = Wire.read();
return 0;
}

return 1;
}

/* ======================================================================
Function: Plugin_014_si7021_startConv
Purpose : return temperature or humidity measured
Input : data type SI7021_READ_HUM or SI7021_READ_TEMP
current config resolution
Output : 0 if okay
Comments: internal values of temp and rh are set
====================================================================== */
int8_t Plugin_014_si7021_startConv(uint8_t datatype, uint8_t resolution)
{
long data;
uint16_t raw ;
uint8_t checksum,tmp;
uint8_t error;

//Request a reading
Wire.beginTransmission(SI7021_I2C_ADDRESS);
Wire.write(datatype);
Wire.endTransmission();

// Tried clock streching and looping until no NACK from SI7021 to know
// when conversion's done. None have worked so far !!!
// I fade up, I'm waiting maximum conversion time + 1ms, this works !!
if (resolution == SI7021_RESOLUTION_11T_11RH)
delay(4);
else if (resolution == SI7021_RESOLUTION_12T_08RH)
delay(5);
else if (resolution == SI7021_RESOLUTION_13T_10RH)
delay(8);
else
delay(12);

/*
// Wait for data to become available, device will NACK during conversion
tmp = 0;
do
{
// Request device
Wire.beginTransmission(SI7021_I2C_ADDRESS);
//Wire.write(SI7021_READ_REG);
error = Wire.endTransmission(true);
delay(1);
}
// always use time out in loop to avoid potential lockup (here 12ms max)
// https://www.silabs.com/Support%20Documents/TechnicalDocs/Si7021-A20.pdf page 5
while(error!=0 && tmp++<=12 );
*/
Wire.requestFrom(SI7021_I2C_ADDRESS, 3);
while ( Wire.available()<3 ) {
}

// Comes back in three bytes, data(MSB) / data(LSB) / Checksum
raw = ((uint16_t) Wire.read()) << 8;
raw |= Wire.read();
checksum = Wire.read();

// Check CRC of data received
if(Plugin_014_si7021_checkCRC(raw, checksum) != 0) {
String log = F("SI7021 : checksum error!");
addLog(LOG_LEVEL_INFO,log);
return -1;
}

// Humidity
if (datatype == SI7021_MEASURE_HUM) {
// Convert value to Himidity percent
data = ((125 * (long)raw) >> 16) - 6;

// Datasheet says doing this check
if (data>100) data = 100;
if (data<0) data = 0;

// save value
si7021_humidity = (uint8_t) data;

// Temperature
} else {
// Convert value to Temperature (*100)
// for 23.45C value will be 2345
data = ((17572 * (long)raw) >> 16) - 4685;

// save value
si7021_temperature = (int16_t) data;
}

return 0;
}


/* ======================================================================
Function: Plugin_014_si7021_readValues
Purpose : read temperature and humidity from SI7021 sensor
Input : current config resolution
Output : 0 if okay
Comments: -
====================================================================== */
int8_t Plugin_014_si7021_readValues(uint8_t resolution)
{
int8_t error = 0;

// start humidity conversion
error |= Plugin_014_si7021_startConv(SI7021_MEASURE_HUM, resolution);

// start temperature conversion
error |= Plugin_014_si7021_startConv(SI7021_MEASURE_TEMP, resolution);

return error;
}

/* ======================================================================
Function: Plugin_014_si7021_setResolution
Purpose : Sets the sensor resolution to one of four levels
Input : see #define default is SI7021_RESOLUTION_14T_12RH
Output : 0 if okay
Comments: -
====================================================================== */
int8_t Plugin_014_si7021_setResolution(uint8_t res)
{
uint8_t reg;
uint8_t error;

// Get the current register value
error = Plugin_014_si7021_readRegister(&reg);
if ( error == 0) {
// remove resolution bits
reg &= SI7021_RESOLUTION_MASK ;

// Prepare to write to the register value
Wire.beginTransmission(SI7021_I2C_ADDRESS);
Wire.write(SI7021_WRITE_REG);

// Write the new resolution bits but clear unused before
Wire.write(reg | ( res &= ~SI7021_RESOLUTION_MASK) );
return (int8_t) Wire.endTransmission();
}

return error;
}
Loading

0 comments on commit d1c53e7

Please sign in to comment.