The i.MX RT 10xx includes a temperature monitor module (TEMPMON) that allows interrupts to be generated if the core temperature exceeds two programmable high temperature levels or falls below a low programmable lower limit level.
Software can also read the present die temperature at any time.
In order for it to work correctly it needs the bandgap reference to be enabled, plus the 480MHz PLL and the 32kHz RTC modules to be operating.
The temperature monitor is factory calibrated and the calibration values can be read from the HW_OCOTP_ANA1 registers. These are used by software to extrapolate the temperature and also to correctly set temperature limits.
The support in the µTasker project is enabled with the define SUPPORT_TEMPMON which adds an interface to read the core temperature via the ADC API in a compatible manner for projects that also run on processors that use ADC based temperature reading.
An example of reading the temperature periodically can be activated in ADC_Timers.h by activating the define ADC_INTERNAL_TEMPERATURE when using the ADC reference. For compatibility the ADC API is used with the input set to
adc_setup.int_adc_bit = ADC_TEMP_SENSOR; // ADC internal temperature
which is how ADC based temperature reading is performed.
Although there is no interrupt generated when the measurement has completed such an interrupt is emulated so that applications remain compatible. The only difference is that the result returned when collecting the value is in °C x 100 (allowing hundredth of degree resolution) and not the raw ADC value itself. Therefore the only modification at the application level is to remove any HW specific conversion that may originally have been performed and use the result directly (or after modification to the desired form). The following shows retrieving and rounding to 1°C resolution:
ADC_SETUP adc_setup; // interrupt configuration parameters
ADC_RESULTS results;
adc_setup.int_type = ADC_INTERRUPT; // identifier
adc_setup.int_adc_mode = (ADC_READ_ONLY | ADC_GET_RESULT);
adc_setup.int_adc_controller = 0;
adc_setup.int_adc_result = &results;
fnConfigureInterrupt((void *)&adc_setup);
results.sADC_value[0] += 50;
results.sADC_value[0] /= 100; // the approximate temperature
rounded up/down to 1°C
fnDebugDec(results.sADC_value[0], DISPLAY_NEGATIVE);
fnDebugMsg(" degC\r\n");
In this particular case the conversion was started previously and it shows just the subsequent retrieval. The conversion was started using the standard API for the ADC with the ADC_TEMP_SENSOR defined as input. When multiple ADC controllers are implemented in the i.MX RT the same one should be referenced for the conversion and retrieval, although there is only one TEMPMON module shared by both and the ADC controller is not actually used.
