Mailbag - PCF8591 I2C 8 bit ADC/DAC Driver - Part 2

ESP Basic series -  I2C driver example for the PCF8591 I2C 8-bit A/D and D/A converter - PART2

For a deeper description of the PCF8591 and simple DAC driver example please go to PART 1



 What we will need:

• ESP8266 nEXT EVO Board  ( Bare PCB available directly at DirtyPCB's Shop )
• PCF8591 Module like the one from here or here, advertised as new versions.
• For programming and uploading the driver and the software we will use the ESPBasic

    Connection with the ESP8266 nEXT EVO Board is very easy, as PCF8591 Module connector is fully compatible with the nEXT Bus connector.


Driver implementation
As been a I2C compatible device you need to have a standard I2C Bus Initialisation function as usual and also to know the I2C address of the device.  
For a detailed PCF 8591 Control Byte description go to PART1.


Software: 

1. Main program: 
 

let address = 72   'PCF8591 I2C Address
i2c.setup(4,5)       'choose your I2C bus pins

cls
let dac = 0
let dac_v = 0
let adc0_1 = 0
let adc0_v = 0
let v_cal = 0.0128

adc0_1 = "ADC stopped"

wprint " <b>PCF8591 8-bit A/D and D/A converter driver demo</b><br><i>by tech@esp8266-projects.com</i><br><br> "

wprint " Input DAC value"
textbox dac

button " Set Value ",[SetDAC]

wprint " <br>DAC Output (V)"
textbox dac_v

wprint "<br>"

wprint "<br><br>ADC0 Read Value:"
textbox adc0_1

wprint "<br>ADC0 Read (Volt):"
textbox adc0_v
wprint "<br><br>"
 
button " Start ADC_0 ",[ADC0]
button " Stop ADC", [Exit ADC]

wprint "<br><br>"
button " Stop Program", [Exit]

wait

2. Set DAC subroutine: 

 [SetDAC]
dac_v = dac * v_cal

i2c.begin(address)
i2c.write(64)  'DAC Enable
delay 5
i2c.write(dac)
i2c.end()
wait

3. Enable ADC subroutine:

[ADC0]
timer 1000, [readADC]
wait

 
4. Read ADC subroutine:
 

[readADC]
ch = 64
i2c.begin(address)               'start another transaction
i2c.write(ch)                         'point to the ADC_0 - keep DAC ON
delay 5
i2c.end()                                'end write transaction

i2c.begin(address)                 'start another transaction
i2c.requestfrom(address,2)    'start a transaction to read 2 bytes
delay 5
adc0_0 = i2c.read()              'read the 1st byte
adc0_1 = i2c.read()              'read the 2nd byte
i2c.end()                                'end read transaction
adc0_v = v_cal + adc0_1 * v_cal
wait

 
5. EXIT ADC subroutine:
 

[Exit ADC]
timer 0
adc0_1 = "ADC stopped"
wait

 
6. Exit Program button subroutine:
 

[Exit]
timer 0
end

 
In the ESP Basic Web editor interface Type & Save your program as "PCF8591.bas" and Run it.  

If all OK the result should look as below: