Error Writing 16 bits to I2C register: Code for HDC1008/HDC1000 humidity sensor from TI

Device Code
1

Hi,

I am trying to interface HDC1008 with imp002. For making a reading , I have to write 0x0000 at the address 0x02 and then read the humidity from address 0x01. While it works on Arduino and WICED, it throws an I2C read error -6 with imp. Any suggestions on how to resolve this error will be helpful! I have added the code and datasheet.

`

//initialize I2C

hardware.i2c12.configure(CLOCK_SPEED_100_KHZ);

//read humidity sensor
function read_humidity()
{
local bytes=hardware.i2c12.read(0x82, “\x01”, 2);
local z=hardware.i2c12.readerror();
server.log(z); //prints -6 on running this code
server.log(bytes);
if (typeof(bytes)!= “string”)
{
//server.log("i2c read error: "+bytes);
return;
}
local data_low = bytes[0];
data_low = data_low << 8;
local data_high = bytes[1];

local humidity= data_low+data_high;
 
humidity=humidity/65536;
server.log("Humidity:"+humidity);
return humidity;

}

//initialize humidity sensor
function humidity_init()
{
local y;

y=hardware.i2c12.write(0x82, "\\x02"+ "\\x00"+"\\x00");  
server.log(y); //prints 0
y=hardware.i2c12.write(0x82, "\\x01");
server.log(y); //prints 0
imp.wakeup(1, read_humidity);

}
humidity_init();

`

2

From what I have understood while debugging, the 16 bit write operation is not happening properly. This operation configures the chip for the subsequent read operation.

3

What’s the intention of the second write() in humidity_init()?

4

I’m a newbie at i2c, but shouldn’t the base address be 0x80 based upon the documentation?

5

I think it depends on how he has it the chip’s two address select pins wired up, @hvacspei, but changing the address to 0x80 is certainly something to try, I’d say.

6

Hi,

Its wired in such a way that the address becomes 0x82. The following code worked out:

`

//initialize I2C
hardware.i2c12.configure(CLOCK_SPEED_100_KHZ);

//read humidity sensor
function read_humidity()
{
hardware.i2c12.write(0x82, “\x01”);
imp.sleep(1);
local bytes=hardware.i2c12.read(0x82, “”, 2);
server.log(bytes);
if (typeof(bytes)!= “string”)
{
//server.log("i2c read error: "+bytes);
return;
}
local data_low = bytes[0];
data_low = data_low << 8;
local data_high = bytes[1];
local humidity= data_low+data_high;
humidity=humidity/655.36;
server.log(“Humidity:”+humidity);
imp.wakeup(1, read_humidity);
return humidity;
}

//initialize humidity sensor
function sensor_init()
{

hardware.i2c12.write(0x82, "");
local y;
y=hardware.i2c12.write(0x82, "\\x02"+"\\x00"+"\\x00");
server.log(y);

local bytes=hardware.i2c12.read(0x82, "\\xFC", 2);
server.log(bytes);

imp.sleep(2);

}
sensor_init();
read_humidity();

`

7

Ah, the datasheet says that after writing the address pointer you must wait the conversion time (or wait for DRDY).

You should be able to change your imp.sleep(1) to imp.sleep(0.00635) - table 7.5 says 6.35ms is the max time for a 14-bit conversion.

8

Yes a delay of 6.35ms works. Thanks for the suggestion!