PCF8575 Does not work with my code....

[CuriousOne]

The all 3 addr pins are connected to GND, which, according to the manual, should give write address of 64. However, it has zero response to my code. Wiring is correct and ports are configured properly. Anyways, here's the complete code - I'm just trying to enable and disable all outputs at same time each 2 seconds.

;----[16F1937 Hardware Configuration]-------------------------------------------
#IF __PROCESSOR__ = "16F1937"
  #DEFINE MCU_FOUND 1
#CONFIG
cfg1 = _FOSC_INTOSC           ; INTOSC oscillator: I/O function on CLKIN pin
cfg1&= _WDTE_OFF              ; WDT disabled
cfg1&= _PWRTE_OFF             ; PWRT disabled
cfg1&= _MCLRE_OFF             ; MCLR/VPP pin function is digital input
cfg1&= _CP_ON                 ; Program memory code protection is enabled
cfg1&= _CPD_OFF               ; Data memory code protection is disabled
cfg1&= _BOREN_OFF             ; Brown-out Reset disabled
cfg1&= _CLKOUTEN_OFF          ; CLKOUT function is disabled. I/O or oscillator function on the CLKOUT pin
cfg1&= _IESO_ON               ; Internal/External Switchover mode is enabled
cfg1&= _FCMEN_ON              ; Fail-Safe Clock Monitor is enabled
  __CONFIG _CONFIG1, cfg1


cfg2 = _WRT_OFF               ; Write protection off
cfg2&= _VCAPEN_OFF            ; All VCAP pin functionality is disabled
cfg2&= _PLLEN_OFF             ; 4x PLL disabled
cfg2&= _STVREN_ON             ; Stack Overflow or Underflow will cause a Reset
cfg2&= _BORV_19               ; Brown-out Reset Voltage (Vbor), low trip point selected.
cfg2&= _LVP_OFF               ; High-voltage on MCLR/VPP must be used for programming
  __CONFIG _CONFIG2, cfg2


#ENDCONFIG


#ENDIF


;----[Verify Configs have been specified for Selected Processor]----------------
;       Note: Only include this routine once, after all #CONFIG blocks
#IFNDEF MCU_FOUND
  #ERROR "No CONFIGs found for [" + __PROCESSOR__ +"]"
#ENDIF


'nixie led clock electronics direct drive


DEFINE LCD_DREG PORTC  
DEFINE LCD_DBIT 4  
DEFINE LCD_RSREG PORTD  
DEFINE LCD_RSBIT 6  
DEFINE LCD_EREG PORTC  
DEFINE LCD_EBIT 3  
DEFINE LCD_BITS 4  
DEFINE LCD_LINES 2  
DEFINE LCD_COMMANDUS 1500  
DEFINE LCD_DATAUS 200
DEFINE ADC_BITS 10       ' Set number of bits in result
DEFINE ADC_CLOCK 3     ' Set clock source (rc = 3)
DEFINE ADC_SAMPLEUS 50 ' Set sampling time in microseconds 


 
ADCON1=%11110011 'enable adc internal reference and justify
FVRCON=%11001111   'set internal reference to 4.096V
OSCCON=%01110101  'SET INTOSC TO 8MHZ
ANSELE=%00000000 'enable adc input porte.2
ANSELA=%00000000 'disable ADC on A
ANSELB=%00000000 'disable ADC on B
ANSELD=%00000000 'disable ADC on D
TRISC=%00000000 'set PORTC as output all
TRISD=%00000000 'set PORTD as output all
TRISB=%00000000 'set PORTB as output all
TRISA=%00000000 'set PORTA 2 as input, others as output
TRISE=%00000000  'set PORTE as output all
WPUB=%00000000 'DISABLE B PULL UPS
OPTION_REG=%100000000 
LCDCON=%00000000  'disable LCD controller pins
LCDSE0=%00000000
LCDSE1=%00000000
LCDSE2=%00000000


DEFINE OSC 8 'set oscillator speed  




SCLM VAR PORTC.7: SDAM VAR PORTC.0  'pcf pins


drk:
I2CWRITE SDAM,SCLM,%01000000,0,[%11111111,%11111111] 'enable outputs
pause 2000      
I2CWRITE SDAM,SCLM,%01000000,0,[%00000000,%00000000] 'disable outputs
pause 2000


goto drk

Any ideas?

[aerostar]

Possibly one of the address lines is dry joint so wrong address.

Found this on forum which could be useful

https://www.picbasic.co.uk/forum/sho...C-Ping-program

[tumbleweed]

Commands to the PCF should be an even number of bytes (one for each port), and you seem to be showing 3.
What's the extra byte after the address?

[CuriousOne]

I tried to "bruteforce" all possible address locations - no change.

The extra byte is write statement, as said in datasheet?

[aerostar]

PBP handles the read write bit if I remember correctly, leave your 0 out

this is my code

ADDR=78 PORTBYTE IS VALUE FOR PORTBITS

i2cwrite sda,scl,ADDR,PORTBYTE 'ENSURE ALL OFF ON POWER UP

So I think your code should be

I2CWRITE SDAM,SCLM,%01000000,[%11111111,%11111111] 'enable outputs

[aerostar]

Meant to have said my code is for the 8 port version, the 16 port version would have another byte added after, as you have got.

"The extra byte is write statement, as said in datasheet?"

Your extra byte is a bit not byte.

[CuriousOne]

Yes, with 8574 I also had no issues....

[tumbleweed]

So I think your code should be

I2CWRITE SDAM,SCLM,%01000000,[%11111111,%11111111] 'enable outputs

That looks correct to me (an even number of bytes, one for each port), and matches the datasheet shown in post #4.

[CuriousOne]

I think there is a hardware issue.
That code works with standalone module with PCF8575. But does not work with the chip directly soldered to my PCB, so I will swap the IC today later and see, if there's any difference.

[CuriousOne]

I figured out the reason, and it is not the code.
For some reason, PCF8575 can't drive ULN2803.
When I run it alone, outputs change as they should do
but when I connect output to ULN2803, output voltage of PCF8575 changes only from 0 to 0.6 volts and ULN2803 does not open.

[CuriousOne]

Solved.
Output current of PCF8575 is not enough to drive ULN2803, so I had to add 2.2K pull-up resistors, and now it works just fine.

[Ioannis]

It makes no sense. From datasheet, page 7 and figures 6 and 10, seems that the 8575 can drive more than 25mA.

I am sure that ULN needs much less than that. Maybe you have a faulty chip? Be very careful with static discharge (ESD) problems.

Ioannis

[richard]

It makes no sense. From datasheet, page 7 and figures 6 and 10, seems that the 8575 can drive more than 25mA.

no , it can sink 25mA ,source 300uA

[Ioannis]

Correct! But what about the charts on page 7?

Ioannis

[CuriousOne]

I measured short circuit current of PCF8575 outputs. It is roughly 0.16mA.

[richard]

Correct! But what about the charts on page 7?

perhaps you should write to them , the graphs in figures 8,9 and 10 are questionable . perhaps the scale should be uA not mA

[Ioannis]

I measured short circuit current of PCF8575 outputs. It is roughly 0.16mA.

The ULN2803 needs at least 0.35mA, so practically 8575 cannot drive it with enough current.

perhaps you should write to them , the graphs in figures 8,9 and 10 are questionable . perhaps the scale should be uA not mA

Seems the datasheet has many errors...

Ioannis

[CuriousOne]

Yes it has problems pulling it up, but it has no problems pulling it down, so I added 2.2K resistor from input of ULN to +5V and now it can be controlled with PC8575.

[DaveP]

Unless you need I2C for comm, why not use something like a UCN5842 and run with shiftout? I have used these for at least 10 years...

[CuriousOne]

I need space saving package, but still solderable by hand, and 16 outputs and low price
These UCNs are large (not available in TSSOP package) and have only 8 outputs....