MAX1247 4-Channel, 12-Bit ADC


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  1. #1
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    Default MAX1247 4-Channel, 12-Bit ADC

    Hello All!

    Has anyone had any experience with this chip? Any PBP code snippets would be greatly appreciated (Spec sheet is not much help w/PBP)!

    Thanks!

  2. #2
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    Default OK, What am I missing?

    I have scoured all of my resources and have come up with the following code but I seem to be missing something. Can anyone provide some insight?

    ' Set compiler to use HS (20 mHz)
    @ DEVICE HS_OSC
    DEFINE OSC 20 'resonator frequency at 20 Mhz

    ' Define the LCD Hookup parameters
    ' data pins D4-D7 are hooked to pins C.0-C.3, respectively
    define LCD_DREG PORTC 'Data Port = PORTC
    define LCD_DBIT 0 'Data starting bit = 0
    define LCD_RSREG PORTC 'Register Select Port = PORTC
    define LCD_RSBIT 4 'RS bit = PortC.4
    define LCD_EREG PORTC 'Enable Port = PORTC
    Define LCD_EBIT 5 'Enable Bit = PortC.5
    define LCD_BITS 4 'LCD Bus Size = 4
    define LCD_LINES 2 'Number of lines on LCD

    define SHIFT_PAUSEUS 1000 '

    Pause 1000 ' Wait for LCD to startup
    Lcdout $FE, $80, "MAX1247"
    lcdout $FE, $C0, "Example"
    pause 1000

    'Variables for ADC
    CB var byte
    CB0 var Byte
    CB1 var Byte
    CB2 var Byte
    CB3 var Byte

    ADResult var word ' contains the result of the read
    X var byte ' counter

    'Control Byte Setup:
    ' Bit 7: Start Bit = 1
    ' Bit 6: Channel Select Bit 2 (SEL2) -See Channel Selection Below
    ' Bit 5: SEL1
    ' Bit 4: SEL0
    ' Bit 3: UNI/BIP - 1=Unipolar 0=Bipolar
    ' Bit 2: SNGL/DIF - 1=Single Ended 0=Differential
    ' Bit 1: PD1 - Sets clock and power down mode
    ' Bit 0: PD0 - Sets clock and power down mode

    'Channel Selection:
    ' SEL2 SEL1 SEL0
    'CH0 0 0 1
    'CH1 1 0 1
    'CH2 0 1 0
    'CH3 1 1 0

    ' To read channel 0 in Unipolar, single ended, external clock mode,
    ' Control Byte (CB) = 10011111
    CB0 = %10011111 'To Read Channel 0
    CB1 = %11011111 'To read channel 1
    CB2 = %10101111 'To read Channel 2
    CB3 = %11101111 'To read Channel 3

    ' Set up MAX1247 4-channel 12-bit ADC
    CLKpin var PORTA.0 'SPI clock pin
    CSpin var PORTA.1 'DAC chip select
    DINpin var PORTA.2 'Data in pin
    DOUTpin var PORTA.3 'Data Out Pin

    'set up Max1247 pins
    TRISA.0 = 0 'CLKpin as output
    TRISA.1 = 0 'CSpin as output
    TRISA.2 = 0 'DINpin as output
    TRISA.3 = 1 'DOUTpin as input

    'Take Reading
    CB = CB0 'Read Channel 0
    Loop:
    CSpin = 1 'keep max1247 off until called
    clkpin = 0 'keep clock low until ready

    gosub ReadADC

    Lcdout $FE, 1 ' Clear LCD screen

    Lcdout $FE, $80, #ADresult

    pause 330
    goto loop

    ReadADC:
    'Send Control Byte
    low CSpin 'cs going low starts the conversion process
    shiftout doutpin, clkpin, 1, [cb\8]
    high cspin
    pause 10

    'Read Result
    adresult = 0
    low cspin
    shiftin dinpin, clkpin, 0, [adresult\12]
    high cspin

    return

    end

  3. #3
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    Default

    try..
    Code:
    ReadADC:
            'Send Control Byte
        low CSpin 'cs going low starts the conversion process
        shiftout doutpin, clkpin, 1, [cb\8]
            'Read Adc
        shiftin dinpin, clkpin, 0, [adresult\12]
        high cspin
    
        return
    Steve

    It's not a bug, it's a random feature.
    There's no problem, only learning opportunities.

  4. #4
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    Default

    Steve - Thanks for your reply (again). Unfortunately, the suggestion did not work. I have attached my board layout. It is pretty straight forward - Do you see anything I am missing? Ignore the other chip - it is a 12-bit D-A chip that works fine... Just can't get the input side of this to work. You will see that I have a pot supplying a voltage to CH0 of the MAX1247. I am trying to read this and display the result on the LCD.

    Thanks!
    Attached Images Attached Images

  5. #5
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    Default

    First observation, you have to disable ADCs on PORTA
    ADCON1=7

    and at the top, you should insert a short PAUSE (let's say 50) after
    CSpin = 1
    Just for safety sake


    sorry i'm too lazy tonight to check the whole thing

    Fortunately, someone else may have a deeper look to?
    Steve

    It's not a bug, it's a random feature.
    There's no problem, only learning opportunities.

  6. #6
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    Default

    Steve - I was really hoping that the ADCON1 thing was it as I missed that one, but still no go. I did the 50 mS pause you recommended, too.

    I can't help but think this is one of those "can't see the forest through the trees" thing. I'm sure it's staring me right in the face. I am using a 12 bit D/A (4-channel) chip (MAX525) on this board as well and it works perfectly. Can't imagine why the A/D chip is giving me such a hard time...

    Let me know if you think of anything else! Thanks!

  7. #7
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    Default

    Attached is code used with a 16F877 and Max 1270 a/d,similar I believe.
    Attached Files Attached Files

  8. #8
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    Arniepj - Thanks for the code! I will give it a try (with some modifications, of course). I will let you know how it goes...

    Thanks!

  9. #9
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    Talking IT WORKS!!! (almost)

    Arniepj - Tried your code and am now actually able to get a reading!!! It is off by about 200 mV but it might be because I am using a 4.096 Vref reference (were you using one?). I will play with this a little more to tweek it so that it is accurate and post the final code. What I have now that works is posted below. The other thing that I changed based on your code was going from an external to internal clock on the Control Byte for the chip.

    Thanks a million!!!

    (and thanks to you too, Steve!)


    ' Set compiler to use HS (20 mHz)
    @ DEVICE HS_OSC
    DEFINE OSC 20 'resonator frequency at 20 Mhz
    ADCON1 = 7 ' Disable PORTA Analog

    ' Define the LCD Hookup parameters
    ' data pins D4-D7 are hooked to pins C.0-C.3, respectively
    define LCD_DREG PORTC 'Data Port = PORTC
    define LCD_DBIT 0 'Data starting bit = 0
    define LCD_RSREG PORTC 'Register Select Port = PORTC
    define LCD_RSBIT 4 'RS bit = PortC.4
    define LCD_EREG PORTC 'Enable Port = PORTC
    Define LCD_EBIT 5 'Enable Bit = PortC.5
    define LCD_BITS 4 'LCD Bus Size = 4
    define LCD_LINES 2 'Number of lines on LCD

    Pause 1000 ' Wait for LCD to startup
    Lcdout $fe, $80, "MAX1247"
    lcdout $fe, $C0, "Example"
    pause 1000
    Lcdout $FE, 1 ' Clear LCD screen

    'Variables for ADC
    CB var byte
    CB0 var Byte
    CB1 var Byte
    CB2 var Byte
    CB3 var Byte

    'Control Byte Setup:
    ' Bit 7: Start Bit = 1
    ' Bit 6: Channel Select Bit 2 (SEL2) -See Channel Selection Below
    ' Bit 5: SEL1
    ' Bit 4: SEL0
    ' Bit 3: UNI/BIP - 1=Unipolar 0=Bipolar
    ' Bit 2: SNGL/DIF - 1=Single Ended 0=Differential
    ' Bit 1: PD1 - Sets clock and power down mode
    ' Bit 0: PD0 - Sets clock and power down mode
    ' 00 - full power down
    ' 01 - fast power down
    ' 10 - internal clock mode
    ' 11 - external clock mode

    'Channel Selection:
    ' SEL2 SEL1 SEL0
    'CH0 0 0 1
    'CH1 1 0 1
    'CH2 0 1 0
    'CH3 1 1 0

    ' To read channel 0 in Unipolar, single ended, internal clock mode,
    ' Control Byte (CB) = 10011110
    CB0 = %10011110 'To read Channel 0
    CB1 = %11011110 'To read Channel 1
    CB2 = %10101110 'To read Channel 2
    CB3 = %11101110 'To read Channel 3

    ' Set up MAX1247 4-channel 12-bit ADC
    CLKpin var PORTA.0 'SPI clock pin
    CSpin var PORTA.1 'DAC chip select
    DINpin var PORTA.2 'Data in pin
    DOUTpin var PORTA.3 'Data Out Pin

    'set up Max1247 pins
    TRISA.0 = 0 'CLKpin as output
    TRISA.1 = 0 'CSpin as output
    TRISA.2 = 0 'DIpin as output
    TRISA.3 = 1 'DOpin as input

    ' ******** Declarations *******************************
    Voltage1 var word
    Voltage2 var word
    Voltage3 var word
    Voltage4 var word
    SerialDataOut var byte ' Serial data out to Max1247 A/D
    SerialDataIn var word ' Serial data in from Max1247 A/D
    Indexer var byte ' Loop indexer for data in

    ' ********* Presets ****************************
    SerialDataOut = cb0
    SerialDataIn = 0
    clkpin = 0 ' Clock signal
    cspin = 0 ' Chip select: low selects
    dinpin = 0 ' Serial data out
    doutpin = 0 ' Serial data in

    '******Main Program ********************************
    DataOut:
    gosub DataAcquisition 'Read data from Max1247
    Voltage1 = SerialDataIn * 2 ' Convert data to voltage
    Voltage2 = (SerialDataIn * 4)/10 ' Convert data to voltage
    Voltage3 = (SerialDataIn * 4)/100 ' Convert data to voltage
    Voltage4 = Voltage1 + Voltage2 + Voltage3 + 9 ' Convert data to voltage
    lcdout $FE, $80, #Voltage4, " " ' Display data
    SerialDataIn = 0
    goto Dataout

    '************ Data Acquisition ***************************
    DataAcquisition:
    for Indexer = 7 to 0 step -1 ' Output data,8 clock pulses
    dinpin = SerialDataOut.0[Indexer] ' Output data port
    pulsout clkpin,5 ' Output clock pulse
    next Indexer ' Next data bit,next clock pulse

    for Indexer = 1 to 12 ' Read data,12 clock pulses
    SerialDataIn = SerialDataIn * 2 ' Shift each bit to the left
    SerialDataIn = SerialDataIn + doutpin ' Data in port
    pulsout clkpin,5 ' Output clock pulse
    next Indexer ' Next data bit,next clock pulse

    return

    end

  10. #10
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    Talking Final Version

    Hello All - Here is the final version of the software. Note that I am using a 2.5V Vref with the MAX1247, so you will have to change the voltage calculation if you are using a different Vref or none at all.

    Enjoy!

    ' Set compiler to use HS (20 mHz)
    @ DEVICE HS_OSC
    DEFINE OSC 20 'resonator frequency at 20 Mhz
    ADCON1 = 7 ' Disable PORTA Analog

    ' Define the LCD Hookup parameters
    ' data pins D4-D7 are hooked to pins C.0-C.3, respectively
    define LCD_DREG PORTC 'Data Port = PORTC
    define LCD_DBIT 0 'Data starting bit = 0
    define LCD_RSREG PORTC 'Register Select Port = PORTC
    define LCD_RSBIT 4 'RS bit = PortC.4
    define LCD_EREG PORTC 'Enable Port = PORTC
    Define LCD_EBIT 5 'Enable Bit = PortC.5
    define LCD_BITS 4 'LCD Bus Size = 4
    define LCD_LINES 2 'Number of lines on LCD

    Pause 1000 ' Wait for LCD to startup
    Lcdout $fe, $80, "MAX1247"
    lcdout $fe, $C0, "Example"
    pause 1000
    Lcdout $FE, 1 ' Clear LCD screen

    'Variables for ADC
    CB var byte
    CB0 var Byte
    CB1 var Byte
    CB2 var Byte
    CB3 var Byte

    'Control Byte Setup:
    ' Bit 7: Start Bit = 1
    ' Bit 6: Channel Select Bit 2 (SEL2) -See Channel Selection Below
    ' Bit 5: SEL1
    ' Bit 4: SEL0
    ' Bit 3: UNI/BIP - 1=Unipolar 0=Bipolar
    ' Bit 2: SNGL/DIF - 1=Single Ended 0=Differential
    ' Bit 1: PD1 - Sets clock and power down mode
    ' Bit 0: PD0 - Sets clock and power down mode
    ' 00 - full power down
    ' 01 - fast power down
    ' 10 - internal clock mode
    ' 11 - external clock mode

    'Channel Selection:
    ' SEL2 SEL1 SEL0
    'CH0 0 0 1
    'CH1 1 0 1
    'CH2 0 1 0
    'CH3 1 1 0

    ' To read channel 0 in Unipolar, single ended, internal clock mode,
    ' Control Byte (CB) = 10011110
    CB0 = %10011110 'To read Channel 0
    CB1 = %11011110 'To read Channel 1
    CB2 = %10101110 'To read Channel 2
    CB3 = %11101110 'To read Channel 3

    ' Set up MAX1247 4-channel 12-bit ADC
    CLKpin var PORTA.0 'SPI clock pin
    CSpin var PORTA.1 'DAC chip select
    DINpin var PORTA.2 'Data in pin
    DOUTpin var PORTA.3 'Data Out Pin

    'set up Max1247 pins
    TRISA.0 = 0 'CLKpin as output
    TRISA.1 = 0 'CSpin as output
    TRISA.2 = 0 'DIpin as output
    TRISA.3 = 1 'DOpin as input

    ' ******************************** Declarations ********************************************
    Voltage var word
    SerialDataOut var byte ' Serial data out to Max1247 A/D
    SerialDataIn var word ' Serial data in from Max1247 A/D
    Indexer var byte ' Loop indexer for data in

    ' ******************************** Presets ************************************************
    SerialDataOut = cb0
    SerialDataIn = 0
    clkpin = 0 ' Clock signal
    cspin = 0 ' Chip select: low selects
    dinpin = 0 ' Serial data out
    doutpin = 0 ' Serial data in

    '********************************* Main Program *********************************************
    DataOut:
    gosub DataAcquisition ' Read data from Max1247
    lcdout $FE, $80, #Serialdatain, " " ' Display data
    lcdout $FE, $C0, #voltage, " " ' Display calculated voltage
    goto Dataout

    '******************************** Data Acquisition ***************************
    DataAcquisition:
    SerialDataIn = 0
    for Indexer = 7 to 0 step -1 ' Output data,8 clock pulses
    dinpin = SerialDataOut.0[Indexer] ' Output data port
    pulsout clkpin,5 ' Output clock pulse
    next Indexer ' Next data bit,next clock pulse

    for Indexer = 1 to 12 ' Read data,12 clock pulses
    SerialDataIn = SerialDataIn * 2 ' Shift each bit to the left
    SerialDataIn = SerialDataIn + doutpin ' Data in port
    pulsout clkpin,5 ' Output clock pulse
    next Indexer ' Next data bit,next clock pulse

    SerialDataIn = SerialDataIn * 2 ' Shift each bit to the left

    'Using a 2.5V Reference with ADC, therefore, 2500 / 4096 = 0.6 mV per step
    'Multiply the result (SerialDataIn) by 6
    voltage = serialdatain * 6
    voltage = voltage / 10 'shift decimal point

    return

    end

  11. #11
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    Atom050,
    Glad to help.An alternative is to use the hardware spi,but since you had a board already,changing i/o might not be possible.

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