Multiplexer channel selection

[Acetronics2]

hi,

your answer is "something like that"

... but as the PIC will perform the A/D conversion ... a Porta Analog input has some good chance to be in use ... if you do not use another ADC input ( PortE 0,1 or 2 for a 16F877a )


without any headaches ... it gives

Porta.5 = 0                ' Enable the Mpxer

for I = 0 to 15

 Porta =  (Porta & %11000001 ) + (I *2)  ' Keep Porta.5 low, Porta.0,6,7 as is, and Porta1-4 select the input
 Pause 5                               ' to stabilize Mpxer Output voltage
 ADCin Portx.y, value[I]           ' Portx.y is where the Mpxer output is connected ...
                                           'value[I] is the table location corresponding to the cell
NEXT I

.
.
.

too simple !

Alain

PS: May be someone could explain me why writing [] with UPPERCASE I inside the brackets show

[I]

...

[skimask]

PS: May be someone could explain me why writing [] with UPPERCASE I inside the brackets show

[I]

...

Italics vs. Italics

Italics vs. [ I ] Italics [ / I ]

http://www.phpbb.com/community/faq.php?mode=bbcode

[Acetronics2]

Italics vs. Italics

Italics vs. [ I ] Italics [ / I ]

Hi, Ski

Yes ... Ok, But ALSO inside a CODE window ...???

could we talk about a BUGGGGGGGGG ????

Alain

[skimask]

Yes ... Ok, But ALSO inside a CODE window ...???
could we talk about a BUGGGGGGGGG ????

I don't know if it's a bug or not. Maybe bbCode doesn't handle nested tokens, or at least that nested token correctly, maybe it was intended to be that way.

[Castor]

Please stay on topic.

Here's a summary: I have two pesky devices in my circuit. A multiplexer and a decoder.The multiplexer is connected as:

MUX
'------------
'RA5	INH
'RA1	A
'RA2	B
'RA3	C
'RA4	D
'------------

notice how the selection channels are on consecutive pins thus making things easy for selecting the channels:

'mux channel selection
'low inh_mux
'for i= 0 to 15
'       Porta =  (Porta & %11000001 ) + (i *2)	'port masking for cycle purposes
'next i

On the other hand the decoder pins are scattered across PORT B and PORTC:

'DCD
'----------
'RE2	G1,G2	
'RB7	A
'RB6	B
'RB5	C
'RC6	D

here's the code i've devised:

'dcd channel selection
low g_dcd
for i=0 to 15
	portb = (portb & %00011111 ) + (i rev  3)<<5
	portc = (portc & %10111111 ) + (i<<3)
next i

The PORTB pins selection works fine (meaning lines A, B and C of the decoder behave as I expected). But line D (the only one on PORTC) gives me a headache. Am I missing something in the mask ?

[skimask]

Please stay on topic.

Guess what? Free help! Deal with it.

'dcd channel selection
low g_dcd
for i=0 to 15
	portb = (portb & %00011111 ) | ( ( i rev  3 ) << 5 )
	portc = (portc & %10111111 ) | ( i << 3 )
next i

OR don't ADD

[Acetronics2]

Guess what? Free help! Deal with it.

'dcd channel selection
low g_dcd

for i=0 to 15
	portb = (portb & %00011111 ) | ( ( i rev  3 ) << 5 )
	portc = (portc & %10111111 ) | ( i << 3 )
next i

OR don't ADD

to get rid of the i lower bits for portC ...

i would have used

portc = (portc & %10111111 ) | ( i.3 << 6 )

but, it's me ...

Alain

[Castor]

... but as the PIC will perform the A/D conversion ... a Porta Analog input has some good chance to be in use ... if you do not use another ADC input ( PortE 0,1 or 2 for a 16F877a )

Hey, thanks for the great answer.
It works like a charm. In fact I use a 16 bit external A/D converter so using PORTA pins as digital I/O doesn't pose an issue. What if the selection pins are scattered across two ports ? Can I get around that without selecting each and every output manually ? Or reworking the board ? (I didn't quite think about channel selection when I built it)

'DCD
'----------
'RE2 G1,G2
'RB7 A
'RB6 B
'RB5 C
'RC6 D

[Acetronics2]

What if the selection pins are scattered across two ports ?

Why not ...

you'll have to write two lines for Ports masking instead of one !

Can I get around that without selecting each and every output manually ? Or reworking the board ?

if you have a pot or button available and a free Pic input or two ... you can easily make the manual channel selection "by soft" ...

(I didn't quite think about channel selection when I built it)

but , may be, you'll have to add a small board on the existing one ( in french : une impériale !!! )

Alain