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This solution was provided by forum member Barak and uses the internal Timer3 interrupt flag CCP2IF. There is no software inside the interrupt, instead the software waits in a loop for CCP2IF to be set and then takes the required action. This approach provides a fixed interval and avoids having a large amount of code inside an interrupt routine and any need to save registers.
Here is Barak's solution.
You can generate ADC with fixed interval with the Special Event Trigger. Example for 18FXXK20 running at 64MHz with 200uS interval:
Code:
SpecialEvent_setup: CCP2CON = %00001011 ' set for trigger special event ADC T3CON = %10111000 ' set timer 3 as clock source for CCP2 and prescale 1:8 Symbol TMR3ON = T3CON.0 ' Timer 3 enable on bit Symbol CCP2IF = PIR2.0 ' CCP2 interrupt flag bit Symbol CCP2Reg = CCPR2.Word ' alias for CCP2 registers CCP2Reg = $190 ' load CCP2 registers with 400 for 200uS sampling/Fs=5KHz ADC_Setup: ADCON0 = %00001100 ' CHS<3:0> 0011 for AN3 ADCON1 = %00000000 ' VSS -ref and VDD +ref. ADCON2 = %00010110 ' Bit 7=0 left justify, bit 5-3 = ACQT 4 TAD, bits 2-0 = Fosc/64 Symbol ADON = ADCON0.0 ' ADC enable bit Symbol GO_DONE = ADCON0.1 ' ADC status bit cleared after acq Process: While 1 = 1 GoSub ADCEvent ' wait for the next CCP2 event ' Process here ' you have less than 200uS to calculate and process ' before going back to the top of the loop to wait ' for the next ADC Event Wend ADCEvent: While CCP2IF = 0 : Wend ' Poll the CCP2 interrupt flag CCP2IF = 0 ' clear the flag for next time While GO_DONE = 1 : Wend ' Poll the GO_DONE flag for completion of conversion Samp = ADRESH ' load 8 MSB from AN3 conversion to variable Return
Using PDS with SPI GLCD based on ST7565R Controller
Graphic LCDs based on the ST7565 are cheaper then GLCDs with other controllers. SPI requires only four pins. If the circuit