;********************************************************************************************* ;* Software License Agreement * ;* The software supplied herewith by Microchip Technology Incorporated * ;* (the "Company") is intended and supplied to you, the Company's * ;* customer, for use solely and exclusively on Microchip products. * ;* * ;* The software is owned by the Company and/or its supplier, and is * ;* protected under applicable copyright laws. All rights are reserved. * ;* Any use in violation of the foregoing restrictions may subject the * ;* user to criminal sanctions under applicable laws, as well as to * ;* civil liability for the breach of the terms and conditions of this * ;* license. * ;* * ;* THIS SOFTWARE IS PROVIDED IN AN "AS IS" CONDITION. NO WARRANTIES, * ;* WHETHER EXPRESS, IMPLIED OR STATU-TORY, INCLUDING, BUT NOT LIMITED * ;* TO, IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A * ;* PARTICULAR PURPOSE APPLY TO THIS SOFTWARE. THE COMPANY SHALL NOT, * ;* IN ANY CIRCUMSTANCES, BE LIABLE FOR SPECIAL, INCIDENTAL OR * ;* CONSEQUENTIAL DAMAGES, FOR ANY REASON WHATSOEVER. * ;* * ;********************************************************************************************* ;***** ADC state machine * ;* The ADC statemachine monitors the current supply voltage by measuring the voltage across * ;* a silicon diode. An ADC value of 20hex is typical for a 5-5.5VDC supply voltage. An ADC * ;* value of 48hex is typical for a 3-3.5VDC supply voltage. Based on the measured diode * ;* voltage, a conversion factor is calculated CF = (ADC*6 - 11) / 256. The conversion factor* ;* is a value between 166 and 232. When multiplied by the intensity and doubled, the value * ;* is a supply voltage corrected duty cycle. * ;* A new conversion factor is calculated by the state machine 10 times a second and the * ;* current duty cycle is corrected on the next pass. If the intensity is changed external to* ;* the state machine, then the int_chng flag notifies the state machine to convert the new * ;* intensity value. * ;* if the ADC value exceeds 2A hex, then the VDD voltage is too low and the state machine * ;* shuts down the system. * ;* * ;* ADC State machine design * ;* Execution indexed state machine * ;* * ;* State * ;* 0 Idle wait state * ;* 1 Convert do battery voltage conversion * ;* 2 Calculate correct intensity for battery voltage * ;* 3 LowBattery shut down state * ;* * ;* * ;* STATE TO STATE TRANSITIONS * ;* From Conditional if True if False comments * ;* ----------------------------------------------------------------------------------------- * ;* Idle if intensity change Calculate Idle waiting * ;* Idle if convert timer timeout Convert Idle * ;* Idle if intensity change Calculate Idle * ;* Convert none Calculate * ;* Calculate none Idle * ;* LowBattery shutdown * ;* * ;* * ;* ACTIONS * ;* Idle none * ;* Convert set PWM output high and convert battery voltage * ;* Calculate using ADC of battery convert intensity to duty cycle * ;* LowBattery shutdown * ;* * ;* INPUT/OUTPUT * ;* input output * ;* Idle ADC_skip_timer, Intensity_change none * ;* Convert ADC, dutycycle ADRESH * ;* Calculate Intensity, ADRESH dutycycle * ;* LowBattery none none * ;* * ;* Math functions * ;* * ;* DATA For Buck system * ;* VDC ADC Max PWM CF * ;* 4.0 2E .337 100% * ;* 4.5 29 .385 91% * ;* 5.0 25 .435 80% * ;* 5.5 21 .483 72% * ;* 6.0 1E .535 65% * ;* * ;* Maximum intensity @ 350 mV * ;* * ;* Conversion factor = (ADC*6 - 0B) * ;* Duty cycle = Scaling value * Intensity * 2 / 256 * ;* * ;********************************************************************************************* ADC ; start of ADC state machine btfsc tstats,doadc ; check for the flag from the skip timer goto ADC_decode ; if set then do decode ; btfss istats,new_int ; check for intensity change return ; if clear then return nop ADC_decode movlw 0xFC ; do sanity check on state variable andwf adc_state,w btfss STATUS,Z goto adc_error ; if larger than 3 then error movlw adc_sm_tab/0x100 ; compute the address of the state in the jump table movwf PCLATH movf adc_state,w andlw 0x03 ; Only four states so 0-3 are only legal values addlw adc_sm_tab movwf PCL ; jump to state jump adc_sm_tab goto ADC_Idle ; idle state goto ADC_Cnvrt ; Perform ADC conversion goto ADC_Calc ; calculate change in intensity goto ADC_LoBatt ; Low Battery shut down adc_error bsf estats,adc_err return ;********************************************************************************************* ;***** ADC_Idle ; this state determines if an ADC conversion is needed btfsc tstats,doadc goto adc_convert btfsc istats,new_int ; if just intensity change, then goto calculation state goto adc_calculate return adc_convert movlw A_Cnvrt ; if time for a conversion, then goto conversion state movwf adc_state return adc_calculate movlw A_Calc ; or if their was just an intensity change. movwf adc_state return ;********************************************************************************************* ;***** Perform ADC conversion state (includes calculation of compensation value) ADC_Cnvrt btfss GPIO,pwm ; determine the current state of the PWM output goto pwm_low pwm_high ; if the PWM is high, then no delay before the conversion call do_adc_nowait goto end_adc_cnvrt pwm_low ; if low, it must be set high during the conversion and bsf GPIO,pwm ; the aquisition time must be added prior to start of conversion call do_adc_wait bcf GPIO,pwm ; after the conversion is complete, the output must be driven low again end_adc_cnvrt movf ADRESH,w ; check for overflow and limit ADC value movwf multa movlw 0x2F ; value must be <=2F, if not then battery is too low subwf multa,w btfss STATUS,C goto math_convert movlw A_Shutdn ; if value is too high, VDD too low, goto shut down state movwf adc_state return math_convert movlw 0xFF movwf dead_count movlw A_Calc ; next state should use the conversion factor to scale current intensity movwf adc_state movlw 0x06 ; multiply ADC value by 6 movwf multb call Multiply movlw 0x0B ; subtract B3 from result subwf lsbyte,w btfss STATUS,C ; if borrow then decrement MSB decf msbyte,f movwf cnv_factor ; store the result in the conversion factor variable movf msbyte,f ; test MSB for overflow btfsc STATUS,Z return ; if non then return movlw 0xFF ; if overflow then max out duty cycle movwf cnv_factor return ;********************************************************************************************* ;***** Compensate intensity value for change in battery voltage ADC_Calc ; this state uses the conversion factor to compensate the intensity bcf STATUS,C rlf intensity,w ; double intensity setting for a 0-7F range movwf multa movf cnv_factor,w ; multiply it by the conversion factor movwf multb call Multiply movf msbyte,w ; move the result into the duty cycle variable btfsc msbyte,7 ; if the result was greater than 7F, then reset to the max duty cycle movlw 0x7F movwf dutycycle bcf tstats,doadc ; clear both initiating variables bcf istats,new_int movlw A_Idle ; and go back to the idle state movwf adc_state bcf istats,new_int ; if just intensity change, then goto calculation state return ;********************************************************************************************* ;***** Low battery detected state ADC_LoBatt decfsz dead_count,f return movlw 0x20 ; reset dead counter for recovery movwf dead_count movlw A_Idle ; upon recovery, goto the idle state. movwf adc_state M_shutdown ;********************************************************************************************* ;***** ADC conversion routine with and without settling time delay ;* with settling time is needed if pwm output was low at the time of the test ;* without settling time is needed if pwm output was high at the time of the test do_adc_wait goto $+1 ; 9.5 uS aquisition time goto $+1 goto $+1 goto $+1 goto $+1 goto $+1 ; 9.5 uS aquisition time goto $+1 goto $+1 goto $+1 goto $+1 do_adc_nowait bsf ADCON0,GO ; start ADC conversion do_adc_test btfsc ADCON0,GO ; test for the end of conversion goto do_adc_test return ;********************************************************************************************* ;***** 8 by 8 multiply routine M_mult macro bit btfsc multa,bit addwf msbyte,f rrf msbyte,f rrf lsbyte,f endm Multiply clrf msbyte clrf lsbyte movf multb,W bcf STATUS,C M_mult 0 M_mult 1 M_mult 2 M_mult 3 M_mult 4 M_mult 5 M_mult 6 M_mult 7 return