I have 2.048V refrance connected to the ADCREFIN pin, pin 54 on the QFP, and I have set up the adc as recommended:
void InitAdc(void)
{
extern void DSP28x_usDelay(Uint32 Count);
// *IMPORTANT*
// The ADC_cal function, which copies the ADC calibration values from TI reserved
// OTP into the ADCREFSEL and ADCOFFTRIM registers, occurs automatically in the
// Boot ROM. If the boot ROM code is bypassed during the debug process, the
// following function MUST be called for the ADC to function according
// to specification. The clocks to the ADC MUST be enabled before calling this
// function.
// See the device data manual and/or the ADC Reference
// Manual for more information.
EALLOW;
SysCtrlRegs.PCLKCR0.bit.ADCENCLK = 1;
ADC_cal();
//SysCtrlRegs.PCLKCR0.bit.ADCENCLK = 0;
EDIS;
// To powerup the ADC the ADCENCLK bit should be set first to enable
// clocks, followed by powering up the bandgap, reference circuitry, and ADC core.
// Before the first conversion is performed a 5ms delay must be observed
// after power up to give all analog circuits time to power up and settle
// Please note that for the delay function below to operate correctly the
// CPU_RATE define statement in the DSP2833x_Examples.h file must
// contain the correct CPU clock period in nanoseconds.
AdcRegs.ADCREFSEL.bit.REF_SEL=1; //2.048v ext ref ***must be before bandgap is powered
AdcRegs.ADCTRL3.all = 0x00E0; // Power up bandgap/reference/ADC circuits
DELAY_US(ADC_usDELAY); // Delay before converting ADC channels
}
Problem is this made no difference, I am still getting readings equivalent to the internal 3V reference (about 740uV/count). The reading does not change even if I comment out the ADCREFSEL line.
Anyone know whats going on?
