I trying to generate a sine wave on the DAC output.
I have the sine wave table stored in the DAC buffer.
Everything works, except the DAC updates much faster than I want despite what values I use for PDB0_DACINT0 or PIT_LDVAL0. It seems to be updating at about 25 MHz.
Any suggestions?
uint16_t buf[16] ={2047, 2429, 2754, 2970, 3047, 2970, 2754, 2429, 2047, 1664, 1339,1123, 1047, 1123, 1339, 1664}; // Sine wave buffer int i; uint8_t *p; // enable clock to DAC (pg. 289) SIM_SCGC2 |= SIM_SCGC2_DAC0_MASK ; // enable DAC, use DACREF_2 (wasn't getting output using DACREF_1) DAC0_C0 |= DAC_C0_DACEN_MASK | DAC_C0_DACRFS_MASK; DAC0_C1 |= DAC_C1_DACBFEN_MASK; p = (uint8_t*)0x400cc000; for(i=0; i < 16; i++) { *p = (buf[i] & 0xff); p++; *p = (buf[i] & 0xf00) >> 8; p++; } // Now we need to setup trigger. SIM_SCGC6 |= SIM_SCGC6_PDB_MASK | SIM_SCGC6_PIT_MASK; // enable clock to PDB and PIT. // PIT module doc pg 1071 PIT_LDVAL0 = 10000; // don't seem to do what I expect PIT_TCTRL0 |= PIT_TCTRL_TEN_MASK; // Enable PIT timer PIT_MCR &= ~PIT_MCR_MDIS_MASK; // enable PIT Timer (pg. 1074) // Now tell PDB to look for PIT0 // PDB Doc on pg. 913 // Select PIT as trigger // PDB0_SC register doc on pg. 920. // Triggers defined on pg. 131 0b0100 is PIT CH 0 PDB0_SC |= PDB_SC_TRGSEL(4) | PDB_SC_PDBEN_MASK; PDB0_DACINT0 = 0xff; // changing this doesn't change update rate as I would expect PDB0_DACINTC0 |= 1; // DAC Interval Trigger enable
