How to get proper data from MCP3464 ADC - Getting just 0x3F30, 0x7F30, 0x1F30

Projects Networking, Protocols, and Devices
1

I'm using MCP3464(8-single channels) for getting the digital count via the SPI. Now in this I have configured the first 2 channels(CH0 and CH1) for getting the digital output, and the setup is providing current to the channels via a 4-20mA Jig (created from the Hardware team in my Office and it has conversion current to voltage conversion cards added to it and the count will go from 0.6V to 3V - I have checking the voltage detection via the Multimeter and it is being received on the ADC channel pins) - even if i switch off the Jig I'm just getting the same 3 values as mentioned in the title in random order and no changing of the current from the jig is making a difference.

-> Here's the code that I'm working on Right now (Using 16-bit data output right now)

int16_t Analog_ADDOn_SPI_Write(uint8_t regAddr, uint8_t data)
{
    uint8_t databuff[2] = {0};
    int16_t ret = ERROR_VAL;

    databuff[0] = (((MCP3464_DEV_ID & 0x03) << 6) | ((regAddr & 0x0F ) << 2) | (MCP3464_WRITE & 0x03) << 0);
    databuff[1] = data;

    pthread_mutex_lock(&SPIbus_mutex);
    SPIBus_ChipSelect(eAnalogAddOn, ENABLE);

    ret = SPIBus_Write(databuff,2);

    SPIBus_ChipSelect(eAnalogAddOn, DISABLE);
    pthread_mutex_unlock(&SPIbus_mutex);
    DEBUG_LOGPRINT("\r\n WRITE - ADDRESS 0x%x, 0th and 1st byte 0x%x 0x%x \r\n", regAddr, databuff[0], databuff[1]);

    return ret;
}

int16_t Analog_ADDOn_SPI_Read(uint8_t regAddr, uint8_t* received_rx_value)
{
    int16_t ret = ERROR_VAL;
    float voltage = 0.0;

    // --------------- 16-bits Code ---------------
    int16_t adc16 = 0x00;     // Output of the ADC will be signed, so use 'int' instead of 'uint'
    uint16_t length = 3;
    uint8_t tx[3] = {0}, rx[3] = {0};

    tx[0] = (((MCP3464_DEV_ID & 0x03) << 6) | ((regAddr & 0x0F) << 2) | (MCP3464_INCREMENTAL_READ & 0x03) << 0);
    tx[1] = 0x00;  // sending dummy bytes for clock pulses
    tx[2] = 0x00;  // for Config3 - 16 bits - 0x80 - only tx0 to tx2 and for Config3 - 32 bits - 0x90 - tx0 to tx4

    Analog_ADDOn_SPI_Write(MCP3464_MUX, 0x08); // here channel0 - 0x08 and channel1 - 0x18
    usleep(2000);

    pthread_mutex_lock(&SPIbus_mutex);
    SPIBus_ChipSelect(eAnalogAddOn, ENABLE);

    ret = SPIBus_Read(tx, rx, length);

    SPIBus_ChipSelect(eAnalogAddOn, DISABLE);
    pthread_mutex_unlock(&SPIbus_mutex);

        adc16 = (rx[1] << 8) | (rx[2] << 0);

    DEBUG_LOGPRINT("\r\n ===== The Value in the 16-bit ADC Variable(Decimal) = %d, (Hexa) - 0x%x and RX Array is 0x%x 0x%x 0x%x ===== \r\n", adc16, adc16, rx[0], rx[1], rx[2]); // Use '(unsigned)adc16' for uint8 or uint16 and use %d as a format specifier.
    DEBUG_PRINT("\r\n");

    return ret;
}

void init_Analog_AddOn(void)
{
    DEBUG_PRINT("\r\n ========== Inside the init_Analog_Addon() function ========== \r\n");

    Analog_ADDOn_SPI_Write(MCP3464_CONFIG0, 0xF3); // changed from 0x33 to 0xF2(standby mode)
    usleep(20000);

    Analog_ADDOn_SPI_Write(MCP3464_CONFIG1, 0x0C); // changed from 0x0C to 0x24
    usleep(20000);

    Analog_ADDOn_SPI_Write(MCP3464_CONFIG2, 0x8B); // from 0x8B to 0x97
    usleep(20000);

    Analog_ADDOn_SPI_Write(MCP3464_CONFIG3, 0xC0);  // 0xC3 - 16-bit, 0xD3 - 32-bit
    usleep(20000);

    Analog_ADDOn_SPI_Write(MCP3464_IRQ, 0x0F); // will always be 0x0C or 0x0D
    usleep(20000);
}

First I am calling the init function and then I'm giving current via my Jig and reading output from the channel0 or channel1. But not getting the required values.

Also sometime getting 0x13, 0x15, 0x17 for the status byte after sending the initial config commands, any help is appreciated, thank you.

2

Can you read register address 0xC?

It should be 0x50.

3

Can you post an annotated schematic showing exactly how you have constructed this. Be sure to show all power sources and the components are labeled. Also post links to the hardware technical specifications and tell us which processor you are using.

4

Is it --?
0x0C

or

0xC0

5

Its my office work setup (working as a firmware engineer) and this hardware was done by a senior hardware engineer and I don't know the full fledged connections and everything cause I just code, but we provide 4 - 20mA via the jig and the current is being observed via the pins on the ADC, when i check via the Multimeter - And the controller used is CC3220SF by TI.

6

sorry for the late reply (time zone difference), Yes I did get 0x50 for reading the register 0x0C.

7

it is 0x0C.

8

Then it is not an SPI problem, the problem is with your "jig"

9

If you can post an annotated schematic and some clear pictures of your jig.

10

I have no programming experience with that processor. Have you tried the TI website for help?

11

Thanks, will check it out.

12

You are getting fixed values because the MCP3464 channel or CONFIG settings are not applied correctly. Ensure CONFIG3 matches your resolution, set MUX before each read with proper conversion delay, and read all bytes according to the selected resolution. Check SPI timing and CS handling, as too-short delays can make the ADC ignore commands.