TMP1075: UnderTemperature Interrupt issues usingTLow on TMP1075

Hi Nathan,

TMP1075 can use the Tlow limit for Under Temperature Alert. Is it possible the device is not in the correct Thermostat Mode (TM)? There is a Comparator mode and an Interrupt mode, and you should ensure the device is in Interrupt mode (TM=1). The Register Map in the datasheet shows which bit in the Configuration register can change TM. 

Best,

Sakeenah

Hello Sakeenah,

Actually, I'm using the device in Interrupt mode.
I also believe my read/write I2C functions are working properly, as the ALERT pin reacts according
to the defined THigh.

Here is how the configuration register is written:

int stats = 0;
uint16_t cfg = 0b0111011011111111; /*
									* One-shot disables
									* Conversion rate set to 220ms
									* 3 fault
									* Alert pin Active High
									* Interrupt mode
									* Continuous conversion
									*/

uint8_t val[2] = {0x00};

val[1] = cfg & 0xff;
val[0] = (cfg >> 8) & 0xff;

stats = TMP_WriteReg(0x01, val);
if (stats != 0){
	DEBUG_MSG("Failed to write config values!");
}

and, to be sure the TLow value convertion from float to uint16_t isn't wrong,
I've also tried the 0,25°C value directly from the datasheet table, instead of a converter number:

// Convert temp from float to uint16
uint16_t t = 0x0040;//(uint16_t)(temp * 16 / 0.0625f);

uint8_t val[2] = {0x00};
val[1] = t & 0xff;
val[0] = (t >> 8) & 0xff;

stats = TMP_WriteReg(0x02, val);
if (stats != 0){
	DEBUG_MSG("Failed to set LowLimit value!");
}

Any ideas why the code above is not working?
PS: I'm using a Freeze Spray to force the scenario described on my first post. Could it be that a drastic/instant
temperature change may cause it not to trigger properly?

Best Regards,
Nathan