A simple logic probe

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basicchip
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A simple logic probe

Post by basicchip » Wed Jun 19, 2019 7:06 pm

Generated by a customer need, a simple logic probe is a great aid in debugging.
probe2.jpg
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This uses a GPIO to detect high or low on the pin, and using weak pull up/down to detect floating lines. And with a normal weak pullup to detect falling edge transitions to show pulsing signals.

Here is the program--

Code: Select all

' Test TIMER0 interrupt
' TIMER0 will interrupt every 2 seconds and print a dot


#if defined LPC1756 || defined LPC1751  || defined LPC1758 || defined LPC4078
 #include "LPC17xx.bas"
#elif defined LPC1114
 #include "LPC11xx.bas"
#elif defined LPC11U37
 #include "LPC11U3x.bas"
#elif defined LPC54102
 #include "LPC54102.bas" 
#elif defined LPC812 
 #error -- use SCTIMER.bas for LPC812
#elif defined LPC2103 || defined LPC2138
  #include "LPC21xx.bas" 
#else
 #error -- your CPU does not support thpinIS feature
#endif

#if defined LPC1751 || defined LPC1756 || defined LPC1758 || defined LPC4078
	#define LED_PIN		74
#elif defined LPC1114
	#define LED_PIN		1	
#elif defined LPC11U68
	#define LED_PIN		1	
#elif defined LPC2138 
	#define LED_PIN		15	
#elif defined LPC54102
	#define LED_PIN		31	
#elif defined LPC54005
	#define LED_PIN		4	
#elif defined LPC2103 
	#define LED_PIN		15
#elif defined SAMD21 
	#define LED_PIN		13
#elif defined MK20DX128 || defined MK20DX256
	#define LED_PIN		13
#elif defined LPC4330
	#define LED_PIN		7	
#elif defined LPC11U37 || defined LPC1137 || defined LPC11U67
	#define LED_PIN		1	
#elif defined LPC1768
	#error need to define an LED pin for thpinIS board
#elif defined LPC2106	
  #error thpinIS code has not been ported to the LPC2106
#else
  #error undefined CPU type    
#endif		   


dim pinISfloating as integer
dim pinIShigh as integer
dim pinIStoggle as integer


INTERRUPT SUB PINT0_IRQ
	pinIStoggle += 1
	GPIO_PIN_IST = 1
ENDSUB



dim TMRintCount			' this provides 1/4 duty cycle for floating indication and timing to sample 

INTERRUPT SUB TIMER0IRQ
	T0_IR = 1	      ' Clear interrupt
#if defined LPC2103 || defined LPC2138
	VICVectAddr = 0 ' Acknowledge Interrupt
#endif
	TMRintCount += 1
	if pinIStoggle then
		OUT(LED_PIN) = TMRintCount AND &H40
		pinIStoggle = 0
	elseif pinISfloating then
		OUT(LED_PIN) = ((TMRintCount AND 3)<>0)
	elseif pinIShigh then
		OUT(LED_PIN) = 0
	else
		OUT(LED_PIN) = 1
	endif
	if TMRintCount =&H80 then TMRintCount = 0
ENDSUB

SUB ON_TIMER ( msec, dothpinIS )
#if defined LPC1756 || defined LPC1751
	TIMER0_ISR   = dothpinIS + 1              'set function of VIC   -- need the +1 for Thumb operation
	T0_PR  = 24999                         '1 ms prescale
	VICIntEnable or= (1<<2)  'Enable interrupt
#elif defined LPC11U37
	TIMER0_ISR   = dothpinIS + 1              'set function of VIC   -- need the +1 for Thumb operation
	SYSCON_SYSAHBCLKCTRL OR= (1<<9)			  ' enable TIMER0
	T0_PR  = 24999                         '1 ms prescale
	VICIntEnable OR= (1<<TIMER0_IRQn)  	 'Enable interrupt
#elif defined LPC1114
	TIMER0_ISR   = dothpinIS + 1              'set function of VIC   -- need the +1 for Thumb operation
	T0_PR  = 49999                         '1 ms prescale
	VICIntEnable or= (1<<19)  'Enable interrupt REMEMBER for LPC11xx we swapped 0/1 with 2/3
#elif defined LPC2103 || defined LPC2138
	VICVectAddr7 = dothpinIS ' set function of VIC 7
	VICVectCntl7 = $25    ' use it for TIMER0 Interrupt:
	VICIntEnable = $20    ' Enable TIMER0 Interrupt
#elif defined LPC54102
	TIMER0_ISR   = dothpinIS + 1              	'set function of VIC   -- need the +1 for Thumb operation
	ASYNCAPBCLKCTRLSET = SYSCON_CLOCK_TIMER0		' enable TIMER0
	T0_PR  = 12499                         	'1 ms prescale
	VICIntEnSet0 = (1<<TIMER0_IRQn) 	 	'Enable interrupt
#else
#endif 
	T0_MR0 = msec-1 ' set up match number of ms
	T0_MCR = 3      ' Interrupt and Reset on MR0
	T0_IR  = 1      ' clear interrupt
	T0_TC  = 0      ' clear timer counter
	T0_TCR = 1      ' TIMER0 Enable
 #if defined LPC2103 || defined LPC2138
	VICVectAddr = 0 ' Acknowledge Interrupt
 #endif
ENDSUB

#ifndef LPC11U37
 #error -- this code has not been ported to other devices yet
#endif


#define TEST_INPUT		61
#define TEST_INT		53					' which interrupt pin
#define TEST_IOCON		IOCON_PIO1_29
#define TEST_PULLDOWN	&H28				' and hystersis
#define TEST_PULLUP		&H30
#define TEST_PULL_MASK	&Hffffffe7


dim wasHIGH

main:

	IO(LED_PIN) = 0				' make it an output
	

	ON_TIMER(2      , ADDRESSOF TIMER0IRQ)			' used to modulate the LED
'	TXD(0)=">"

	SYSCON_PINTSEL(0) = TEST_INT					' interrupt on GPIO1.19
	SYSCON_SYSAHBCLKCTRL OR= ((1<<19) OR (1<<6))	' enable GPIO interrupts

	FLEX_INT0_ISR   = (ADDRESSOF PINT0_IRQ) + 1    	'set function of VIC   -- need the +1 for Thumb operation
	GPIO_PIN_SIENF = 1								' interrupt on falling edges
	VICIntEnable OR= (1<<FLEX_INT0_IRQn) 			'Enable interrupt	
	
	TEST_IOCON = (TEST_IOCON AND TEST_PULL_MASK) OR TEST_PULLUP		' leave it pulled up
      
	WHILE (1)
		if (TMRintCount = 0) then
			wasHIGH = IN(TEST_INPUT)
			if pinIStoggle then
				pinISfloating = 0
'				TXD(0)="T"
'				print pinIStoggle
			elseif wasHIGH then
				TEST_IOCON = (TEST_IOCON AND TEST_PULL_MASK) OR TEST_PULLDOWN	' pin is high, try to pull it weakly low
				if IN(TEST_INPUT) <> wasHIGH then 
					pinISfloating = 1
'					TXD(0)="F"
				else
					pinISfloating = 0
					pinIShigh = 1
	'				TXD(0)="H"
				endif
				TEST_IOCON = (TEST_IOCON AND TEST_PULL_MASK) OR TEST_PULLUP		' leave it pulled up
			else
				pinISfloating = 0
				pinIShigh = 0
'				TXD(0)="L"
			endif
			pinIStoggle = 0
		endif
	LOOP
  
Possible improvements would make toggling indications represent the toggle frequency. Obviously you can't see 1 MHz or even 1 KHz, but it would be nice to flash at different rates. Currently the toggle indication just flashes at a visible rate for both, but some difference in rate would be nice.



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