PCF8574A Port Expander
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I'm trying to unravel the mysteries of the PCF8574A Port Expander.
If I send a byte 255 to the chip does that take all output ports high?
If I send a byte of 1000 0000 or 128 does that take P7 high. I guess I could
put it another way by asking does the chip respond to an input byte just like
any old serial-in parallel-out shift register, with the advantage that you
can read back the state of the parallel ports?
Sid Weaver
W4EKQ
Port Richey, FL
[noparse][[/noparse]Non-text portions of this message have been removed]
If I send a byte 255 to the chip does that take all output ports high?
If I send a byte of 1000 0000 or 128 does that take P7 high. I guess I could
put it another way by asking does the chip respond to an input byte just like
any old serial-in parallel-out shift register, with the advantage that you
can read back the state of the parallel ports?
Sid Weaver
W4EKQ
Port Richey, FL
[noparse][[/noparse]Non-text portions of this message have been removed]
Comments
does work. What I do is send every command twice so that it gets to the
output. All IO through that device is buffered in the chip, so the
first write to the device is forced to the pins by the second.
-- Jon Williams
-- Applications Engineer, Parallax
-- Dallas Office
Original Message
From: Newzed@a... [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=vPdXBa171PlpmHcbQhByc40RI2RsYKDGtKorQ2b0PQZtW2lf91-YintPzEP6hsPx8v7GM00W]Newzed@a...[/url
Sent: Wednesday, April 07, 2004 4:40 PM
To: basicstamps@yahoogroups.com
Subject: [noparse][[/noparse]basicstamps] PCF8574A Port Expander
I'm trying to unravel the mysteries of the PCF8574A Port Expander.
If I send a byte 255 to the chip does that take all output ports high?
If I send a byte of 1000 0000 or 128 does that take P7 high. I guess I
could
put it another way by asking does the chip respond to an input byte just
like
any old serial-in parallel-out shift register, with the advantage that
you
can read back the state of the parallel ports?
Sid Weaver
W4EKQ
Port Richey, FL
jwilliams@p... writes:
> In my opinion the PCF8574A is more hassle than it's worth ... but it
> does work. What I do is send every command twice so that it gets to the
> output. All IO through that device is buffered in the chip, so the
> first write to the device is forced to the pins by the second.
>
Would you have a recommendation for an I2C chip that would perform better? I
notice the "double send" in the program.
Sid
[noparse][[/noparse]Non-text portions of this message have been removed]
behaves more like a standard port in that each bit has a direction
registers. Once you've set the direction bits you can read or write the
ports without hassle. I'll post a simple demo in the files section, and
for those of you that read Nuts & Volts, I've used this part (MCP23016)
to create a two-wire LCD interface in my May column.
-- Jon Williams
-- Applications Engineer, Parallax
-- Dallas Office
Original Message
From: Newzed@a... [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=PmaThJ02cqKxvgKkblOeEO3ZJzOLSKyqwhtFSydy4CJw5tohAmkqEFRmc2oIBAJBWCvjwYj_mw]Newzed@a...[/url
Sent: Thursday, April 08, 2004 7:52 AM
To: basicstamps@yahoogroups.com
Subject: Re: [noparse][[/noparse]basicstamps] PCF8574A Port Expander
In a message dated 4/8/2004 8:48:40 AM Eastern Daylight Time,
jwilliams@p... writes:
> In my opinion the PCF8574A is more hassle than it's worth ... but it
> does work. What I do is send every command twice so that it gets to
> the output. All IO through that device is buffered in the chip, so
> the first write to the device is forced to the pins by the second.
>
Would you have a recommendation for an I2C chip that would perform
better? I
notice the "double send" in the program.
Sid
[noparse][[/noparse]Non-text portions of this message have been removed]
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-- Jon Williams
Original Message
From: Jon Williams
Sent: Thursday, April 08, 2004 8:48 AM
To: basicstamps@yahoogroups.com
Subject: RE: [noparse][[/noparse]basicstamps] PCF8574A Port Expander
Yep -- the MCP23016 is what I use. It's got two ports (16 bits) and
behaves more like a standard port in that each bit has a direction
registers. Once you've set the direction bits you can read or write the
ports without hassle. I'll post a simple demo in the files section, and
for those of you that read Nuts & Volts, I've used this part (MCP23016)
to create a two-wire LCD interface in my May column.
-- Jon Williams
-- Applications Engineer, Parallax
-- Dallas Office
Original Message
From: Newzed@a... [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=VcHk0R6oqhIcQZyIjJa_7yINud3S2fGbyMb8PH9jStc0dZpSxEUYhEEPNAmKT5KYKvk3qpRrpej5]Newzed@a...[/url
Sent: Thursday, April 08, 2004 7:52 AM
To: basicstamps@yahoogroups.com
Subject: Re: [noparse][[/noparse]basicstamps] PCF8574A Port Expander
In a message dated 4/8/2004 8:48:40 AM Eastern Daylight Time,
jwilliams@p... writes:
> In my opinion the PCF8574A is more hassle than it's worth ... but it
> does work. What I do is send every command twice so that it gets to
> the output. All IO through that device is buffered in the chip, so
> the first write to the device is forced to the pins by the second.
>
Would you have a recommendation for an I2C chip that would perform
better? I
notice the "double send" in the program.
Sid
[noparse][[/noparse]Non-text portions of this message have been removed]
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from the same email address that you subscribed. Text in the Subject
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jwilliams@p... writes:
> Yep -- the MCP23016 is what I use. It's got two ports (16 bits) and
> behaves more like a standard port in that each bit has a direction
> registers. Once you've set the direction bits you can read or write the
> ports without hassle. I'll post a simple demo in the files section, and
> for those of you that read Nuts & Volts, I've used this part (MCP23016)
> to create a two-wire LCD interface in my May column.
>
Is the May column in print?
Sid
[noparse][[/noparse]Non-text portions of this message have been removed]
jon.
Do you have some recommented sources for the mcp23016?
Spence
k4kep
-- Jon Williams
-- Applications Engineer, Parallax
-- Dallas Office
Original Message
From: Newzed@a... [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=-LbZMRKQJdpC57jexka7MJMxK5MB2miUhONsLZEI0lHiNosPI_W8CGrEyvq0TpgsyCXVaV9Vx64]Newzed@a...[/url
Sent: Thursday, April 08, 2004 8:53 AM
To: basicstamps@yahoogroups.com
Subject: Re: [noparse][[/noparse]basicstamps] PCF8574A Port Expander
In a message dated 4/8/2004 9:49:57 AM Eastern Daylight Time,
jwilliams@p... writes:
> Yep -- the MCP23016 is what I use. It's got two ports (16 bits) and
> behaves more like a standard port in that each bit has a direction
> registers. Once you've set the direction bits you can read or write
> the ports without hassle. I'll post a simple demo in the files
> section, and for those of you that read Nuts & Volts, I've used this
> part (MCP23016) to create a two-wire LCD interface in my May column.
>
Is the May column in print?
Sid
Component Shop as well.
-- Jon Williams
-- Applications Engineer, Parallax
-- Dallas Office
Original Message
From: BOYD S.(SPENCE) MINER [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=1Hso0x5xSO_Ns0-OT_2mW3i7ouMyrtlIh29kzhAtnytdobPMsL6QayJBnzBRpzEeZrgxCN2qhEkqgQQ]k4kep@b...[/url
Sent: Thursday, April 08, 2004 12:25 PM
To: basicstamps@yahoogroups.com
Subject: [noparse][[/noparse]basicstamps] RE: PCF8574A Port Expander
EXCUSE CAPS
JON.
DO YOU HAVE SOME RECOMMENTED SOURCES FOR THE MCP23016?
SPENCE
K4KEP
does not stock and the minimum order is 400 pieces.
>
Original Message
> From: Jon Williams [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=cAh4ie4jJ-4c8mJ_UHtGwvnYydj0XQfotRMHU8GX8_JNBRF6OxyE9McEGn3SXpHK6Lr3feeuWEguQCFfu_ARTVU]jwilliams@p...[/url
> Sent: April 8, 2004 7:35 PM
> To: basicstamps@yahoogroups.com
> Subject: RE: [noparse][[/noparse]basicstamps] RE: PCF8574A Port Expander
>
>
> Mouser has them; so does Digi-Key. We'll probably be adding them to our
> Component Shop as well.
>
> -- Jon Williams
> -- Applications Engineer, Parallax
> -- Dallas Office
Pat, your referring to Digi's policies on special orders. That's
standard policy with them, I'm afraid. For the Microchip device, not
the Phillips/TI device? I believe Digi is planning on making more
available. Double check them, within a few days.
Gregg C Levine hansolofalcon@w...
"The Force will be with you...Always." Obi-Wan Kenobi
"Use the Force, Luke."· Obi-Wan Kenobi
>
Original Message
> From: PatM [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=t64Vu9tAUIwB2eH33mFuuvKrifMstfnRm22nCeBRFlcSgHKVy4dnqpnRpEGlwVJ7fLuX66Dk]pmeloy@s...[/url
> Sent: Thursday, April 08, 2004 10:41 PM
> To: basicstamps@yahoogroups.com
> Subject: RE: [noparse][[/noparse]basicstamps] RE: PCF8574A Port Expander
>
> Mouser has stock on the 28 pin dips and sells singles. Digikey lists
but
> does not stock and the minimum order is 400 pieces.
>
> >
Original Message
> > From: Jon Williams [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=Fz30rZo3jGm7iKXyb4c-WT_d1tfOWgR3tf6kuya2vsAyrp1TSxHbG7B46kj9U17jXQiTZxhmDy84ns7PRZ8]jwilliams@p...[/url
> > Sent: April 8, 2004 7:35 PM
> > To: basicstamps@yahoogroups.com
> > Subject: RE: [noparse][[/noparse]basicstamps] RE: PCF8574A Port Expander
> >
> >
> > Mouser has them; so does Digi-Key. We'll probably be adding them
to our
> > Component Shop as well.
> >
> > -- Jon Williams
> > -- Applications Engineer, Parallax
> > -- Dallas Office
jwilliams@p... writes:
> Nevermind, the demo is already there: MCP23016.BSP.
>
>
Where is the demo?
Sid
[noparse][[/noparse]Non-text portions of this message have been removed]
-- Jon Williams
-- Applications Engineer, Parallax
-- Dallas Office
Original Message
From: Newzed@a... [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=BPl1cykRnohsRT6nqskk-9J_NNJ1swmHPM9OeEe5kyYe9dXUEvD3SyiQh5XEIkIABDH1A5nPQQoO]Newzed@a...[/url
Sent: Friday, April 09, 2004 7:38 AM
To: basicstamps@yahoogroups.com
Subject: Re: [noparse][[/noparse]basicstamps] PCF8574A Port Expander
In a message dated 4/8/2004 9:06:26 PM Eastern Daylight Time,
jwilliams@p... writes:
> Nevermind, the demo is already there: MCP23016.BSP.
>
>
Where is the demo?
Sid
writes:
Please ignore this post. It was written and posted 3 days ago.
> In a message dated 4/8/2004 9:06:26 PM Eastern Daylight Time,
> jwilliams@p... writes:
>
>
> > Nevermind, the demo is already there: MCP23016.BSP.
> >
> >
>
> Where is the demo?
>
> Sid
>
>
> [noparse][[/noparse]Non-text portions of this message have been removed]
>
>
>
[noparse][[/noparse]Non-text portions of this message have been removed]