# Arduino USB \> Firmata \> I2C \> \[GPIO PCF8574 + MCP23017 + temp BMP280\]

**URL:** <https://discourse.nodered.org/t/arduino-usb-firmata-i2c-gpio-pcf8574-mcp23017-temp-bmp280/24281>\
**Category:** Hardware\
**Created:** [5 April 2020 18:47 UTC](https://discourse.nodered.org/t/arduino-usb-firmata-i2c-gpio-pcf8574-mcp23017-temp-bmp280/24281 "2020-04-05T18:47:51Z")\
**Posts on this page:** 1\
**Showing post:** 22

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**Author:** ![PizzaProgram](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/pizzaprogram/32/19431_2.png) [@PizzaProgram](https://discourse.nodered.org/u/PizzaProgram)\
**Post date:** [23 December 2020 07:48 UTC](https://discourse.nodered.org/t/arduino-usb-firmata-i2c-gpio-pcf8574-mcp23017-temp-bmp280/24281/22 "2020-12-23T07:48:55Z")

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# About MCP23017:

I've realised there is no "all-in-one" solution to do everything combined.  
So I've decided to break into parts:

1. MCP23017 boards will be used with [I2C through a AtTiny85](https://github.com/harbaum/I2C-Tiny-USB/tree/master/digispark) adapter and [one of these nodes](https://flows.nodered.org/search?term=MCP23017).  
Sadly I'll loose the INTERRUPT possibility.

2. I'll drop PCF8574 modules. Use Arduino boards directly only.  
_(Same price\PIN ratio + shielded USB included. A 7 port USB HUB costs \< $5. So it's not worth the trouble.)_

3. Temperature reading will be a completely other thing. Maybe with AtTiny85 boards using a [safe 1wire PJON system and protocol](https://www.pjon.org/).

4. As I've said before: I'll drop Firmata. More trouble than reward.

Closing this topic.

# Follow possible solutions at the new topic:

> [@MQTT with Arduino Nano + NodeRed](https://discourse.nodered.org/t/mqtt-with-arduino-nano-nodered/37351/3):
>
> YES, this is exactly the thing I'm looking for! with minimal C, only "forwarding" RAW data from/to all ports and reconnecting if connection lost. doing whatever possible at NodeRed side. My question is: HOW to do that? Currently I'm investigating this: And This:

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_[View the full topic](https://discourse.nodered.org/t/arduino-usb-firmata-i2c-gpio-pcf8574-mcp23017-temp-bmp280/24281)._