https://github.com/robert-hh/ADS7818

Python class interfacing the ADS7818 AD-converter
https://github.com/robert-hh/ADS7818

Last synced: 2 months ago
JSON representation

Python class interfacing the ADS7818 AD-converter

• Host: GitHub
• URL: https://github.com/robert-hh/ADS7818
• Owner: robert-hh
• Created: 2018-09-23T13:34:01.000Z (almost 6 years ago)
• Default Branch: master
• Last Pushed: 2019-01-01T11:08:08.000Z (over 5 years ago)
• Last Synced: 2024-03-17T15:34:33.390Z (3 months ago)
• Language: Python
• Size: 6.84 KB
• Stars: 0
• Watchers: 3
• Forks: 1
• Open Issues: 0
• Metadata Files:
  • Readme: README.md

Lists

• awesome-micropython - ADS7818 - Python class interfacing the ADS7818 AD-converter. (Libraries / IO)

README

        
# ADS8718: Python class for the ADS7818 AD-converter

This is a very short and simple class. It uses the SPI bus for the interface. That

ensures that the tight timing requirements of the ADS7818 are met.

## Constructor

### adc = ADS7818(spi, \*, baudrate = 1000000, vref = 2.5, inverted = False)

- spi is an SPI object which has to be created by the caller. Just the Pins have to be assigned by the caller.

The init method of the class sets baud rate, phase, polarity and word size.

- baudrate defines the baud rate of the SPI. the default is 1000000.

The valid range is 200kHz through 4 MHz. These boundaries are silently enforced by the class.

- vref is the reference voltage, used to calculate the voltage value. If the internal Vref is used, this allows small

corrections. If an external Vref is applied, it can be assigned here. Vref is only used for the calculation

of the equivalent voltage.

- inverted set True if an inverter is inserted between the MOSI output and CONV input

in order to get an high CONV level during quiet times.

## Methods

### value = adc.value()

Retrieves the adc raw value using the setting of the constructor. The returned

value is in the range of 0 - 4095

### volt = adc.voltage()

Reads the adc value and return the equivalent voltage. This is based on the vref

value set in the constructor. The formula is:   

    voltage = 2 * vref * value / 4096

## Interface

The ADS7818 is connected to the SPI bus signals. There is no CS needed. The

connection consist of:

|Micro|ADS7818|

|:---|:---|

|MOSI|CONV (5)|

|MISO|DATA (6)|

|CLK|CLK (7)|

The ADS7818 needs a Vcc of 5V. For connecting to a 3.3V device, insert a resistor

of about 4.7 kOhm between MISO and DATA.

Device like those of Pycom have low MOSI level. This does not nicely match the

interface description of the ADS7818. In that is a problem, an inverter can be

placed between MOSI and CONV, and the flag inverted has to be set True when calling

the constructor.

## Example

```

# Drive the ADS7818 ADC using SPI

# Connections:

# xxPy | ADS7818

# -----|-------

# P10  |  CLK

# P11  |  CONV

# P14  |  DATA add a series resistor of about 4.7k between DATA and P14

#

from machine import SPI

from ads7818 import ADS7818

spi = SPI(0, SPI.MASTER)

vref = 2.493 # measured at the ADS7818

ads = ADS7818(spi)

while True:

    # start a conversion and get the result back

    value = ads.value()

    volt = 2.0 * vref * value / 4096

    print(value, volt)

    res= input("Next: ")

    if res == "q":

        break

```