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ZHCU759 July 2021

3.1.2 Software

Solution-specific and device-independent files are provided as .c/.h files. The main.c file provides the initialization of the GPIOs, I2C and SPI communication, ADC or DAC setup, PWM setup for the nonsynchronous boost, and power sequencing. The software is required to power up the board properly as well as read the ADC data.

To program the MSP430FR5969-SP independently, make sure no other jumpers are installed and provide an external 3.3 V to J16 (for the external ADC circuit) and J36 (for the integrated ADC solution). This only powers on the MSP430FR5969-SP so that adjustments to the power sequencing are done without damaging the ADC128S102QML-SP.

In main.c the variable "ext_int" is set to either 0 or 1 to run two different functions. When "ext_int" is set to 0, it runs the code to read all the channels from the external ADC via SPI. If "ext_int" is set to 1, the code reads all inputs from the integrated ADC. The ADC reads are done via low power interrupts to save on processing power of the MSP430. The values are then stored in the FRAM and are accessed when the software is paused. Each ADC channel corresponds to a specific point in memory with a memory word length default of 1000 and can be changed via the variable WRITE_SIZE.

Figure 3-1 Software Flow

To access the data in FRAM from Code Composer Studio (CCS), open the memory browser (View → Memory Browser) and type the starting address outlined in Table 3-1 and Table 3-2. Select save memory and save it as a .dat file (this file type can be opened with Microsoft® Excel®). The save memory function allows saving of the data in different formats for different processing requirements. After selecting the file location to save the file, enter the start address and specify the length of the array (default is 1000). Opening the .dat file shows the raw ADC data in column one. To convert the integer values, use the ADC equation (Equation 5) in a column next to the data captured to convert the integer values to voltage, where n is the number of bits used for the measurement.

Equation 5.

A D C c o n v e r s i o n e q u a t i o n = \frac{D i g i t a l O u t p u t \times V_{r e f}}{2^{n}}

Table 3-1 Memory Location and Variable Name: External ADC Configuration

ADC BUFFER	ADC128S102-SP ADC CHANNEL	MEASURED RAIL	MEMORY LOCATION
adc_buffer_0	IN0	500 µA	x004400
adc_buffer_1	IN1	±2 A	x0047E8
adc_buffer_2	IN2	20 V	x004BD0
adc_buffer_3	IN3	Temperature voltage	x004FB8
adc_buffer_4	IN4	±5 V	x0053A0
adc_buffer_5	IN5	40 V	x005788
adc_buffer_6	IN6	0.25 A–1 A	x005B70
adc_buffer_7	IN7	5 V	x005F58

Table 3-2 Memory Location and Variable Name: MSP430™ Configuration

ADC BUFFER	MSP430 ADC12 CHANNEL	MEASURED RAIL	MEMORY LOCATION
adc_buffer_0	A0	500 µA	x004400
adc_buffer_1	A8	40 V	x0047E8
adc_buffer_2	A9	0.25 A–1 A	x004BD0
adc_buffer_3	A10	5 V	x004FB8
adc_buffer_4	A12	±2 A	x0053A0
adc_buffer_5	A13	20 V	x005788
adc_buffer_6	A14	Temperature voltage	x005B70
adc_buffer_7	A15	±5 V	x005F58