MSP430I2040 Not Working

Hi Varaprasad,

If you've measured the voltage at the ADC pins with a multi-meter and they are as you expected then we should be looking at your ADC code instead of the circuitry. Can you provide this code as well as what voltages are being input to the MSP430 and what ADC results you get as compared to what you expect?

Regards,
Ryan

Hi Ryan,

       Thanks for the reply. Below attached are the code and the ADC results. The main purpose of our circuit is to allow user to connect the input in both the directions, which makes the ground as floating.This is done to achieve reverse polarity protection and isolation from the Micro-controller ground. Please let me know if this floating ground is affecting the ADC output. On the firmware side we tried both binary and 2's complement mode. Both are giving random values. 

The code is taken from TI example library and modified:

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/*******************************************************************************
 * MSP430i2xx EUSCI_A UART - Loopback at 115200 Baud
 *
 * Description: In this example, the UART RX and TX pins are connected to
 * create a loopback of communication data. The example shows how to properly
 * initialize UART communication at baud rate of 115200 using SMCLK as the
 * source. After the byte is put into the buffer to send the device goes into
 * LPM until it has received the sent byte. If data corruption occurs then
 * the LED will be turned on indicating a problem.
 *
 *
 * Author: Zack Lalanne
 ******************************************************************************/

#include "driverlib.h"

volatile uint32_t value32 = 0;

int main(void) {
    // Configuration for 9600 UART with SMCLK at 16384000
    // These values were generated using the online tool available at:
    // software-dl.ti.com/.../index.html
    EUSCI_A_UART_initParam uartConfig = {
        EUSCI_A_UART_CLOCKSOURCE_SMCLK,          // SMCLK Clock Source
        106,                                       // BRDIV = 8
        10,                                      // UCxBRF = 14
        206,                                      // UCxBRS = 34
        EUSCI_A_UART_NO_PARITY,                  // No Parity
        EUSCI_A_UART_MSB_FIRST,                  // MSB First
        EUSCI_A_UART_ONE_STOP_BIT,               // One stop bit
        EUSCI_A_UART_MODE,                       // UART mode
        EUSCI_A_UART_OVERSAMPLING_BAUDRATE_GENERATION  // Oversampling Baudrate
    };

    WDT_hold(WDT_BASE);

    // Setting the DCO to use the internal resistor. DCO will be at 16.384MHz
    CS_setupDCO(CS_INTERNAL_RESISTOR);

    // SMCLK should be same speed as DCO. SMCLK = 16.384MHz
    CS_clockSignalInit(CS_SMCLK, CS_CLOCK_DIVIDER_1);

    // Settings P1.2 and P1.3 as UART pins. P1.4 as LED output
    GPIO_setAsPeripheralModuleFunctionInputPin(GPIO_PORT_P1,
                                               GPIO_PIN2 | GPIO_PIN3,
                                               GPIO_PRIMARY_MODULE_FUNCTION);

    // Configure and enable the UART peripheral
    EUSCI_A_UART_init(EUSCI_A0_BASE, &uartConfig);
    EUSCI_A_UART_enable(EUSCI_A0_BASE);

    EUSCI_A_UART_enableInterrupt(EUSCI_A0_BASE,
                                 EUSCI_A_UART_RECEIVE_INTERRUPT);

    // Internal ref
   SD24_init(SD24_BASE, SD24_REF_INTERNAL);

   //Ch0 single mode
   SD24_initConverterAdvancedParam param = { 0 };
   param.converter = SD24_CONVERTER_0;
   param.conversionMode = SD24_SINGLE_MODE;
   param.groupEnable = SD24_NOT_GROUPED;
   param.inputChannel = SD24_INPUT_CH_ANALOG;
   param.dataFormat = SD24_DATA_FORMAT_BINARY;
   param.interruptDelay = SD24_FOURTH_SAMPLE_INTERRUPT;
   param.oversampleRatio = SD24_OVERSAMPLE_256;
   param.gain = SD24_GAIN_1;
   SD24_initConverterAdvanced(SD24_BASE, &param);
   SD24_enableInterrupt(SD24_BASE, SD24_CONVERTER_0, SD24_CONVERTER_INTERRUPT);

  // Delay ~200us for 1.2V ref to settle
  __delay_cycles(3200);


    while(1)
    {
			__no_operation();               // SET BREAKPOINT HERE

			// Go to sleep and wait for user input
			__bis_SR_register(LPM0_bits | GIE);

			SD24_startConverterConversion(SD24_BASE, SD24_CONVERTER_0);

			// Go to sleep and wait for ADC conversion
			__bis_SR_register(LPM0_bits | GIE);

			EUSCI_A_UART_transmitData(EUSCI_A0_BASE, (value32 >> 8));
			EUSCI_A_UART_transmitData(EUSCI_A0_BASE, value32);


			__no_operation();
    }
}

#pragma vector=USCI_A0_VECTOR
__interrupt void USCI_A0_ISR(void)
{
        switch (__even_in_range(UCA0IV, USCI_UART_UCTXCPTIFG)) {
        case USCI_NONE: break;
        case USCI_UART_UCRXIFG:

                EUSCI_A_UART_receiveData(EUSCI_A0_BASE);
                // Leave LPM so next byte can be sent
                __bic_SR_register_on_exit(LPM0_bits);

                break;
        case USCI_UART_UCTXIFG: break;
        case USCI_UART_UCSTTIFG: break;
        case USCI_UART_UCTXCPTIFG: break;
        default: break;
        }
}


#pragma vector=SD24_VECTOR
__interrupt void SD24_ISR(void)
{
        switch (__even_in_range(SD24IV, SD24IV_SD24MEM3))
        {
        case SD24IV_NONE: break;
        case SD24IV_SD24OVIFG: break;
        case SD24IV_SD24MEM0:

        		value32 = SD24_getHighWordResults(SD24_BASE, SD24_CONVERTER_0);

               break;
        case SD24IV_SD24MEM1: break;
        case SD24IV_SD24MEM2: break;
        case SD24IV_SD24MEM3: break;
        default: break;
        }
        __bic_SR_register_on_exit(LPM0_bits);   // Wake up from LPM0
}

	EXPECTED VALUES				ACTUAL VALUES
Vin(V)	Calculated Vout (mV)	Measured Vout (mV)	E-HEX	E-DEC	A-HEX	A-DEC	Vout (mV)	Vdiff (mV)
10	15.129	15.000	844E	33870	645D	25693	-97.160	112.289
9	13.616	13.500	83E0	33760	87A7	34727	26.903	-13.287
8	12.103	12.000	8372	33650	9D2C	40236	102.557	-90.454
7	10.590	10.500	8304	33540	B126	45350	172.787	-162.197
6	9.077	9.000	8295	33429	262E	9774	-315.775	324.852
5	7.564	7.500	8227	33319	82C9	33481	9.792	-2.227
4	6.051	6.000	81B9	33209	F032	61490	394.437	-388.385
3	4.539	4.500	814B	33099	A7A0	42912	139.307	-134.768
2	3.026	3.000	80DD	32989	FDC6	64966	442.172	-439.147
1	1.513	1.500	806F	32879	A9CC	43468	146.942	-145.429
0	0.000	0.000	8000	32768	2EEE	12014	-285.013	285.013
-1	-1.513	-1.500	7F92	32658	C245	49733	232.979	-234.492
-2	-3.026	-3.000	7F24	32548	9816	38934	84.677	-87.703
-3	-4.539	-4.500	7EB6	32438	371C	14108	-256.256	251.718
-4	-6.051	-6.000	7E48	32328	837C	33660	12.250	-18.301
-5	-7.564	-7.500	7DDA	32218	E96D	59757	370.638	-378.202
-6	-9.077	-9.000	7D6C	32108	36C9	14025	-257.396	248.319
-7	-10.590	-10.500	7CFD	31997	FC63	64611	437.297	-447.887
-8	-12.103	-12.000	7C8F	31887	68D0	26832	-81.519	69.416
-9	-13.616	-13.500	7C21	31777	B7AA	47018	195.694	-209.310
-10	-15.129	-15.000	7BB3	31667	3361	13153	-269.371	254.242

Regards,

Varaprasad.

Hi Varaprasad,

I see that you have properly sampled some driverlib examples for your application and as such your code seems to be in working condition. Does Vin accurately represent your differential input voltage (VID)? If so then the full-scale range (FSR) of your input voltage is much too expansive to be handled by the SD24 peripheral. VFSR(+/-) = (+/-)VREF/GAIN. In your case VREF is 1.16 V (typical internal reference value) and your GAIN is 1, the expected VFSR is +/- 1.2 V and the analog input range should not exceed ~80% of that value, or VID = +/- 928 mV in your case. This is all explained in Section 5.6.7 of the MSP430I2040 datasheet.  Please refer to EVMs like the EVM430-I2040S for a better understanding of how the SD24 is intended to operate.

Regards,
Ryan

Hi Ryan,
Thanks for the inputs. The voltage range which we designed is well with in the limits(+/- 928mV) as you can see the voltage divider in the circuit (1V = 1.5mV). What we suspect is, this problem might be because of floating ground. Please suggest if the designed circuit can be used or not.

Regards,
Varaprasad.

I'm having the same issue with my board where do I patch it to fix this issue?