support for PCF8574 ?

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ILoveIOT
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Joined: 01 Nov 2015, 10:54

support for PCF8574 ?

#1 Post by ILoveIOT » 01 Nov 2015, 11:08

First of all,..very nice project,..nice work !!

Is the PCF8574 chip supported, or will it be supported in the future ?
And can I use it with a max of 8 chips on the same I2C bus ?

BerndJ
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Posts: 86
Joined: 28 Sep 2015, 06:57

Re: support for PCF8574 ?

#2 Post by BerndJ » 01 Nov 2015, 12:31

Hi,

they use the 8574 for the lcd display on port 0x27.

Best is u use the MCP23017, double ports and the possibility of 8 pieces.

And, ... it´s running.

Don´t forget the pull-up resistor in the reset line.

BerndJ

Martinus

Re: support for PCF8574 ?

#3 Post by Martinus » 01 Nov 2015, 13:47

ILoveIOT wrote:Is the PCF8574 chip supported, or will it be supported in the future ?
As of R41 it is supported. Only available on development branch on github.
ILoveIOT wrote:And can I use it with a max of 8 chips on the same I2C bus ?
Yes you can. Ports in the webgui are numbered 1-8 for the first chip, 9-16 for the second, etc.

I guess you know how to work with this device. For newbees, we do advice using the MCP23017 because its a lot easier to use. The PCF8574 has sort of open drain outputs, can only source about 100 uA, so active high output is limited. Ouputs are active high after power on, so active high relay boards go immediately to the active state during boot.

And remember that the ESP is not as stable as one would like... So controlling outputs can lead to undesirable effects during unexpected ESP reboots. Just of word of warning... Used as inputs should be OK.

ILoveIOT
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Posts: 44
Joined: 01 Nov 2015, 10:54

Re: support for PCF8574 ?

#4 Post by ILoveIOT » 01 Nov 2015, 14:49

Thank you for the anwsers, I've allot of the PCF8574, so that's why my question, but as you explained,
I will order the MCP23017 chip, and wait a bit ;) Thanks !!

chunter1
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Posts: 82
Joined: 22 Jan 2016, 22:40

Re: support for PCF8574 ?

#5 Post by chunter1 » 06 Feb 2016, 00:12

I got a PCF8574 board here from China.

Image

I jumpered it so that it shows up on address 0x3f (PCF8574, MCP23017, LCD Modules) when scanning the I2C bus.

So far so good.
However, when is set up a task called "Switch input - PCF8574" i don't get any valid status of the corresponding input.
Am i right, that when i set PORT to 1, then i should get the status of the first input?
I tried ports 1..8 but no reaction to signals on any input-pin.

Does anybody know what i am doing wrong?
(I am running build 77)

thanks
chunter

Martinus

Re: support for PCF8574 ?

#6 Post by Martinus » 06 Feb 2016, 10:24

Port numbering depends on the jumper settings. I've updated the Wiki with a table to get the right portnumbers.
http://www.esp8266.nu/index.php/PCF8574#Input

But at the same time, if discovered a bug within the plugin for the PCF8574A and that one does not currently work!
(if your device is recognized at 0x3F, you must have a PCF8574A type)

Will be fixed in R78 (although I can't really test it because I only have the PCF8574 type)

chunter1
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Posts: 82
Joined: 22 Jan 2016, 22:40

Re: support for PCF8574 ?

#7 Post by chunter1 » 06 Feb 2016, 20:57

Thank you very much for the fast update!
Works like a charm in both directions :)

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