Hi, Ian,
From the Fig 43. LLS fit of the temperature sensor output voltage in data sheet of LPC15xx, we can see that the temperature sensor output voltage is about 500mV in room temperature(at 30 degree), in 12 bits ADC format, the ADC result should be 0.5*(3.3V/4095)=620 or 0x26C.
Pls check the following setting.
1)For ADC, ADCx->INSEL=0x03;
2)you have to power up the on-chip temperature:
SYSCON->PDRUNCFG&=~(1<<18);
For detailed inf, pls refer to section 3.6.47 Power configuration register
The PDRUNCFG register controls the power in UM10736.pdf
3)this is the procedure to use ADC to sample analog channel:
31.3.1 Perform a single ADC conversion with the temperature sensor as
ADC input
To perform a single ADC conversion for ADC0 channel 0 using the temperature sensor
output:
1. Enable the temperature sensor output as input to channel 0. See Table 434.
2. Configure the system clock to be 50 MHz and select a CLKDIV value of 0 for a
sampling rate of 50 MHz using the ADC CTRL register.
3. Select the synchronous mode in the CTRL register.
4. Select ADC channel 0 to perform the conversion by setting the CHANNELS bits to
0x1 in the SEQA_CTL register.
5. Set the START bit to 1 in the SEQA_CTRL register.
6. Read the RESULT bits in the DAT0 register for the conversion result.
Hope it canb help you
BR
XiangJun Rong
