DT’s Elapsed Timer Magic Trick

[Amoque]

I am a total noob, but I feel such cleverness deserves a guess - even if only to prove how far superior your skills. I am unwilling to just shrug and wait for you to reveal your skill without so much as voicing the consideration I have given - not so much a joke, but puzzle - you have provided.

I will guess that there is some capacitance in the circuit and that you use some application of the RCTime constant as a reference; different clocks would, I think, reveal the clock speed by the timer values measured when charging and discharging a capacitor from a known voltage. I take my guess from watching the LED (which, I believe has a capacitance associated - and conveniently a resistor in series) which is slow to start - I'm hoping, because it is busy measuring...

[Art]

Interesting idea, but not tested by me so I don’t know if it would work

The virtue in what I’m doing is someone might come up with a better way,
and at the moment I would appreciate that.
It’s not genius trust me, you’ll find out. Someone is close on another forum.

[Demon]

2015 nominee for best computer generated animations.

Robert

[towlerg]

628A has two internal clocks

[Art]

I know of the 4MHz RC clock. What’s the other?

[Art]

It got figured out on another forum. A better way actually, without writing to the on-chip EEPROM at all.

'***********************************************************************************
'*                                                                                 *
'*                    Microchip Pic 16F628 @ 8,16 or 24MHz                         *
'*                                  Art 2015                                       *
'*                                                                                 *
'*                          [email protected]                               *
'*                                                                                 *
'***********************************************************************************
'
'
DEFINE OSC 20								'
DEFINE NO_CLRWDT							'watchdog is cleared manually
'
INCLUDE "Elapsed.bas"							‘modified to take a variable
'
' execution time!
'
'
percount var byte							'
wrtcount var byte							'
clkvalue var byte							'
xdata var byte								'
'oscfreq var word							‘this is declared in Elapsed Timer file
notreset var bit							'
'
CMCON = 7									'set ports digital
trisb.4 = 0									'set led output
portb.4 = 0									'
'
percount = 0								'
clkvalue = 0								'
'
'
notreset = status.bit4						'check wdt reset occured - 0 is did reset
'
'
if notreset = 1 then						'was not reset by watchdog
portb.4 = 1									'turn led on
for percount = 0 to 255						'do eeprom writes until wdt reset
pause 100									'
write percount,$00							'
next percount								'
makereset:									'failsafe to make reset occur
@ nop										;
goto makereset								'
else									'was reset by watchdog
@ clrwdt									;clear the watchdog from now on
wrtcount = 0								'reset write counter
countwrites:								'count eeprom writes
read wrtcount,xdata							'read byte
@ clrwdt									;
pause 10									'
if xdata != $00 then						'
goto donecount								'exit counting loop
endif										'
wrtcount = wrtcount + 1						'increment count
goto countwrites							'
donecount:									'
for percount = 0 to 255						'erase the eeprom for next time
pause 10									'
@ clrwdt									;
write percount,$FF							'
next percount								'
endif										'
'
'gosub flashout								'for testing only
'
oscfreq = 0									'reset oscillator frequency
'
if wrtcount > 8 then						'11 
oscfreq = $B1E7									'set oscillator frequency
endif										'
if wrtcount > 18 then						'21
oscfreq = $63C7								'set oscillator frequency
endif										'
if wrtcount > 27 then						'30
oscfreq = $15A7								'set oscillator frequency
endif										'
'
'
gosub ResetTime								'reset time 00:00:00
gosub StartTimer							'start clock timer
'
'
'
cycle:
@ clrwdt
if Ticks > 49 then
portb.4 = 1
else
portb.4 = 0
endif
goto cycle
'
'
'
flashout:									'flash out the count of eeprom writes before wdt reset
for percount = 0 to wrtcount				'with the red led
portb.4 = 1									'flash rate will still depend on oscillator frequency
pause 250									'at this stage
@ clrwdt									'
pause 350									'
@ clrwdt									'
portb.4 = 0									'
pause 250									'
@ clrwdt									'
pause 350									'
@ clrwdt									'
next percount								'
pause 500									'
@ clrwdt									'
pause 500									'
@ clrwdt									'
pause 500									'
@ clrwdt									'
return										‘
'

[towlerg]

I know of the 4MHz RC clock. What’s the other?

Actually there are three, 4 Mhz and 48Khz internal clocks and the WDT

[Tabsoft]

Pretty clever Art!