Enabling 12bit A/D on 16 series board

by **Timbo** » Mon Apr 13, 2015 8:49 pm

I'm trying to turn on the 12 bit A/D ability of the 16 series pic's

When I say I'm trying, to be honest not very hard at this moment. I need to read the data sheet to see the regs needed but I have tried to look at the lib to see if there was already a switch and where to add the code.

I presume its in the adc module in the Main routine used to do the initialization.

The thing is that you chaps always come through with a little snippet of code when asked so its always worth asking. There may even be some code on the wiki I failed to see.

Thanks

Tim

by **Timbo** » Mon Apr 13, 2015 9:47 pm

Actually looking at the data sheet, it looks pretty simple..

Just need to set AD12B (AD1CON1: bit 10)

by **Jerry Messina** » Mon Apr 13, 2015 11:23 pm

There's a note in the datasheet that states that the ADC module must be disabled before modifying the AD12B bit.

Something like this should work...

Code: Select all: sub main() dim w as uinteger // adc is setup before main starts // set adc to 12-bit mode AD1CON1.bits(15) = 0 // turn off adc (ADON) AD1CON1.bits(10) = 1 // set 12-bit mode (AD12B) AD1CON1.bits(15) = 1 // turn module back on w = adc.read(A0) end sub

by **Timbo** » Tue Apr 14, 2015 6:45 am

Hi, Thanks

Yes I saw that just forgot to mention it when posting, but I really appreciate the code you posted, its not the way I was going to do it which shows I have a lot to learn still.

I may add a new routine that just starts the conversion process. Then at some point later just read the result. I have not looked up the time it takes to do the conversion but as they will mostly be in interrupt code It makes sense not be taking up too much time when it can be done in between interrupts.

Cheers

Tim

by **Jerry Messina** » Tue Apr 14, 2015 11:16 am

If you're triggering the ADC manually it may not be worth the bother of using interrupts to read it.

The conversion time depends on the settings, but normally it's just a few 10's of usec, if that. Eventually your code will have to wait for the ADC to be done or you'll need to go through the complication of setting up a state machine to do the processing. I tend to use interrupts for events that just can't wait, like reading a uart rx input and such, or if triggering the ADC via some hardware method like a timer.

Of course, that's just my opinion, and every situation is different. You may have a good reason for not wanting to wait...

by **Timbo** » Tue Apr 14, 2015 11:54 am

Hi Jerry

The way its going to be used is that I read the A/D converter every say 100hz. I intend to do it during an interrupt. I actually will be reading 2 or 3 Analogue inputs. So will be doing it sequentially via a 1000hz interrupt Tick

If the conversion time is only say 10us then I can do it in the interrupt but if its longer its going to be wasting my time in the interrupt. By starting the conversion in one interrupt tick and reading it in the next, no time is wasted.

My coding on another platform always revolved around doing loads in interrupt code. Really it was just Usart int and a 100hz time. But the timer interrupt had large amounts of code running with many state machines.
For example I had routines that would flash a led x times or time how long a button was down. That way your main code is not stuck timing the flashes and can get on with the real processing.

Here is an example of what I mean. The actual time in the interrupt is really very short as only a few lines of code actually gets run.

Code: Select all: TMR_INTERRUPT: Context Save FSR0L, FSR0H, FSR1L, FSR1H Reset_Bank If TMR1IF = True Then Clear TMR1ON ' STOP THE TIMER TIMER1REG = TIMER1REG + TMR1_VAL ' LOAD TMR1 Set TMR1ON ' START THE TIMER AGAIN If GPSLoadedTimer > 0 Then Dec GPSLoadedTimer ; Every pass we need to check & dec this timer EndIf ; Handle the Vibration and button detection If INT0IF = 1 Then ; Look for a vibration int flag If Vibcounter1 < 200 Then ; keep it in a byte range Inc Vibcounter1 ; Ok seen so up the counter INT0IF = 0 ; Clear the flag EndIf EndIf If Vibcounter1 > 0 Then Inc VibTimer1 ; manage the count down timer to clear the vibration counter If VibTimer1 > 4 Then VibTimer1 = 0 Select Vibcounter1 Case > 100 Vibcounter1 = Vibcounter1 - 10 Case > 50 Vibcounter1 = Vibcounter1 - 5 Case > 20 Vibcounter1 = Vibcounter1 - 2 Case > 0 Dec Vibcounter1 EndSelect EndIf Else VibTimer1 = 0 EndIf If Vibcounter1 > MinVibrationCnt Then ; If the vibration level has been high enough reload or timer If GPSStatus = 1 Then ; And there is currently a valid fix VibOkToLogTimer = InterLogVibTime EndIf EndIf If Vibcounter1 > LedAliveVal Then ; Look after the led off timer LedOffTimer = LedOffTimerPeriod EndIf If WayPointLogButton = 0 Then If PushButtonCnt < 254 Then Inc PushButtonCnt PushButtonReleased = False EndIf Else PushButtonCnt = 0 PushButtonReleased = True EndIf Hz100Tick = 1 ; Handle the second timers Dec Hz100Cnt If Hz100Cnt = 0 Then Hz100Cnt = 100 Btg TwoSecFlag If TwoSecFlag = 1 Then TwoSecondTick = 1 ; Led Brightness Twosecond tick flag EndIf SecondPeriodTimerFlag = 1 ; Every second we set these flags If Uptime < 250 Then Inc Uptime ; Timer used to prevent doing an Eeprom write until the cap has had long enough to charge EndIf ; handle the GPS active timer If MilageAccumelationPeriod > 0 Then Dec MilageAccumelationPeriod EndIf If InvalidFixDelayTimer > 0 Then Dec InvalidFixDelayTimer EndIf If GPSModuleWorkingTimer > 0 Then Dec GPSModuleWorkingTimer GPSModuleWorking = True Else GPSModuleWorking = False LedIndicatorStatus = NoGps GPSDataLoadingInfo = 0 ; We need to clear this so we do not have staggered data EndIf If SflashFullCntr > 0 Then ; Every second we see if we have to dec the memory flash counter Dec SflashFullCntr EndIf If GPSLogPeriodTimer > 0 Then ; Handle our period timer Dec GPSLogPeriodTimer NewLogPeriod = False Else NewLogPeriod = True EndIf If WayPointLogTimer > 0 Then ; The way point timer to control the time between way points being saved Dec WayPointLogTimer EndIf If VibOkToLogTimer > 0 Then ; Decrement our Ok to log timer which is loaded when Dec VibOkToLogTimer ; we see some vibration EndIf If NoFixTimer > 0 Then Dec NoFixTimer EndIf If NoFixShortTimer > 0 Then Dec NoFixShortTimer EndIf If LedOffTimer > 0 Then Dec LedOffTimer EndIf If GPSSpeed >= WarningSpeed Then If OverSpeedTimer > GPSSpeedTimeVal Then Inc OverSpeedTimer Else OverSpeed = 1 EndIf Else OverSpeedTimer = 0 OverSpeed = 0 EndIf If WarningSpeedperiodTimer > 0 Then ; Speed warning timer Dec WarningSpeedperiodTimer EndIf If LogExtendTimer > 0 Then Dec LogExtendTimer EndIf EndIf ; Now handle the Leds If MemoryFull = False Then Select LedIndicatorStatus ; No Gps System Fault Case NoGps If SounderActive = False Then Ledoff EndIf IntLedOn = 0 ; Memory full flash has first hit Case MemoryLowFlash ; Flash mode is Memory Low If FlashCount > 0 Then If InterflashTimer > 0 Then Dec InterflashTimer Else Dec FlashCount If LedStatusToggle = 1 Then If LedsAreOff = 0 Then LedOn IntLedOn = 1 EndIf LedStatusToggle = 0 Else If SounderActive = False Then Ledoff IntLedOn = 0 EndIf LedStatusToggle = 1 EndIf InterflashTimer = FLashPartFullPeriod EndIf Else If GPSStatus = 1 Then ; If the current fix is valid LedIndicatorStatus = GpsWithFix ; return to fix mode Else LedIndicatorStatus = GpsWithNoFix ; return to no fix mode EndIf FlashCount = 0 ; Ensure this is 0 EndIf ; Gps Active But no Fix Case GpsWithNoFix If InterflashTimer > 0 Then Dec InterflashTimer Else If LedStatusToggle = 1 Then If LedsAreOff = 0 Then LedOn IntLedOn = 1 EndIf LedStatusToggle = 0 Else If SounderActive = False Then Ledoff EndIf IntLedOn = 0 LedStatusToggle = 1 EndIf InterflashTimer = GpsWithNoFixFlashPeriod EndIf ; Gps Fixed Case GpsWithFix If LedsAreOff = 0 Then LedOn IntLedOn = 1 EndIf ; Way Point log Case GPSWayPointLog If FlashCount > 0 Then If InterflashTimer > 0 Then Dec InterflashTimer Else Dec FlashCount If LedStatusToggle = 1 Then LedOn LedStatusToggle = 0 IntLedOn = 1 Else Ledoff LedStatusToggle = 1 IntLedOn = 0 EndIf InterflashTimer = GPSWayPointLogFlashPeriod EndIf Else LedIndicatorStatus = GpsWithFix ; Ensure we return to the right mode FlashCount = 0 ; Ensure this is 0 LedStatusToggle = 1 EndIf EndSelect EndIf ; Handle the sounder as required Select SounderIndicatorStatus Case FirstFix If SounderCount > 0 Then SounderOn Dec SounderCount Else SounderOff SounderIndicatorStatus = NoSound EndIf Case NoFixMovingWarning ; When generating a sound we check if the overal time > 0 If SounderCount > 0 Then Dec SounderCount If InterSoundPeriod > 0 Then ; Check the iner toggle period is > 0 Dec InterSoundPeriod Else If SounderActive = True Then ; else toggle it SounderOff Else SounderOn EndIf InterSoundPeriod = InterSoundPeriodVal ; and reload our counter EndIf Else SounderOff SounderIndicatorStatus = NoSound ; Over all time done so set the state to no sound and shut down the sound EndIf Case NoFixMovingShortWarning If SounderCount > 0 Then ; Single beelp type sounds have no toggle section SounderOn Dec SounderCount Else SounderOff SounderIndicatorStatus = NoSound EndIf Case LowMemoryWarning If SounderCount > 0 Then Dec SounderCount If InterSoundPeriod > 0 Then Dec InterSoundPeriod Else If SounderActive = True Then SounderOff Else SounderOn EndIf InterSoundPeriod = InterSoundPeriodVal EndIf Else SounderOff SounderIndicatorStatus = NoSound EndIf Case RemindBusinessTypeWarning ; Toggle between the 2 freqencys for this indicato If SounderCount2 > 0 Then Dec SounderCount2 If InterSoundPeriod > 0 Then Dec InterSoundPeriod Else InterSoundPeriod = InterSoundPeriodVal If SounderActive = True Then SounderOff Else EnableSounderToggle = True Btg SounderFreq SounderOn EndIf EndIf Else SounderOff SounderIndicatorStatus = NoSound EndIf Case WayPointSound Select WayPointWoundStage Case 0 If SounderCount2 > 0 Then ; Dit Dec SounderCount2 SounderOn Else SounderCount2 = WaypointGapTime Inc WayPointWoundStage EndIf Case 1 If SounderCount2 > 0 Then ; space Dec SounderCount2 SounderOff Else SounderCount2 = WaypointSoundTime1 Inc WayPointWoundStage EndIf Case 2 If SounderCount2 > 0 Then ; Dit Dec SounderCount2 SounderOn Else SounderCount2 = WaypointGapTime Inc WayPointWoundStage EndIf Case 3 If SounderCount2 > 0 Then ; space Dec SounderCount2 SounderOff Else SounderCount2 = WaypointSoundTime1 Inc WayPointWoundStage EndIf Case 4 If SounderCount2 > 0 Then ; Dit Dec SounderCount2 SounderOn Else SounderCount2 = WaypointGapTime Inc WayPointWoundStage EndIf Case 5 If SounderCount2 > 0 Then ; space Dec SounderCount2 SounderOff Else SounderCount2 = WaypointSoundTime2 Inc WayPointWoundStage EndIf Case 6 If SounderCount2 > 0 Then ; Deeeee Dec SounderCount2 SounderOn Else SounderOff ; And shut down SounderIndicatorStatus = NoSound EndIf EndSelect EndSelect EndIf Clear TMR1IF ; Clear TMR1 interrupt flag LowIntExit: Context Restore

by **Jerry Messina** » Tue Apr 14, 2015 12:47 pm

See - I knew there'd be a good reason!

> By starting the conversion in one interrupt tick and reading it in the next, no time is wasted.
That sounds like a good idea. I don't like to wait at all inside an ISR since it will block other interrupts unless you set up priorities and that can just make things more complicated. It's not too bad with one or two levels like the PIC18, but much past that and I begin to get myself in trouble!

by **Timbo** » Tue Apr 14, 2015 2:04 pm

Hi Jerry

Thanks thats sound advice I have little or no experience with the 24 series devices. I like not having to learn the hardway

Enabling 12bit A/D on 16 series board

Enabling 12bit A/D on 16 series board

Re: Enabling 12bit A/D on 16 series board

Re: Enabling 12bit A/D on 16 series board

Re: Enabling 12bit A/D on 16 series board

Re: Enabling 12bit A/D on 16 series board

Re: Enabling 12bit A/D on 16 series board

Re: Enabling 12bit A/D on 16 series board

Re: Enabling 12bit A/D on 16 series board

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