Analog Pins

[sprinkfitter]

What is the best way to increase the number of analog pins on an esp8266. I need 4 more Analog pins for sensors. Thank You in advance

[mcauser]

Sounds like you're after an I2C ADC. eg. ADS1115.

https://www.adafruit.com/product/1085
https://www.aliexpress.com/item/I2C-ADS ... 56200.html
$2-15 USD

A few people have written drivers:
* https://bitbucket.org/thesheep/micropython-ads1015/src
* https://github.com/adafruit/micropython ... it-ads1015
* https://github.com/AnthonyKNorman/Micropython_ADS1115
* https://github.com/robert-hh/ads1x15
* https://github.com/coylen/BatteryMonitor

[sprinkfitter]

Can multiplexer like the 74hc4051 be used?

[deshipu]

And if you are using a Wemos D1 Mini, by total coincidence I just started selling my homebrew analog shield: https://www.tindie.com/products/deshipu ... r-d1-mini/

[sprinkfitter]

I have a D1 not the mini. But i might be getting one to try out. Your board looks solid.

[mcauser]

Judging by this page, yes you can use a 74hc4051 multiplexer:
https://internetofhomethings.com/homethings/?p=530

[sprinkfitter]

Thats an Arduino hook up. I wonder if someone has hook it up with Micropython???

[crizeo]

I am using the MCP3008, which works perfectly for up to 8 analog inputs using the SPI pins (~2$). You could also use the MCP3004, I think, but it only has 4 analog inputs. I wrote a simple driver (mcp3008.py):

Code: Select all

from machine import Pin

class MCP3008:
    def __init__(self, clk=14, mosi=13, miso=12, cs=15):
        self._clk = Pin(clk, Pin.OUT)
        self._mosi = Pin(mosi, Pin.OUT)
        self._miso = Pin(miso, Pin.IN)
        self._cs = Pin(cs, Pin.OUT)

    def read(self, channel):
        # """ Reads an analog value from the given channel (0-7) and returns it. """
        if channel not in range(0, 8):
            raise ValueError("channel must be 0-7")

        self._cs(1)  # negative edge
        self._cs(0)
        self._clk(0)

        send_cmd = channel
        send_cmd |= 0b00011000  # 0x18 (start bit + single/ended)

        # send bits (only 5 bits considered)
        for i in range(5):
            self._mosi(bool(send_cmd & 0x10))  # check bit on index 4
            self._clk(1)  # negative edge
            self._clk(0)
            send_cmd <<= 1

        # receive value from MCP
        v = 0
        for i in range(11):
            self._clk(1)  # negative edge
            self._clk(0)
            v <<= 1
            if self._miso():
                v |= 0x01

        return v

The layout of the MCP3008 can be found on the internet (e. g. here).
You will have to make the follwing connections (MCP3004/8 <-> ESP8266):

• V_dd <-> 3.3V
• V_ref <-> 3.3V
• AGND <-> GND
• CLK <-> SCK (14)
• D_out <-> MISO (12)
• D_in <-> MOSI (13)
• CS <-> 15
• DGND <-> GND

Then you can read values from the different channels that can be addressed using integers 0 to 7. Example:

Code: Select all

from mcp3008 import MCP3008
mcp = MCP3008()
print("Value on CH0:", mcp.read(0))

You can change the pins in the constructor if you like (e. g. CS pin can be any pin you like). If you need more than 8 extra ADC inputs, you can probably (not tested) simply connect multiple MCP3008 (on the same three SPI pins), but use a different CS pin for each MCP.

[sprinkfitter]

Thank You for all the info. That helps out a-lot. Great Forum!!!! Thanks again

[sprinkfitter]

Now that work with the MCP3008. Thank You