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  • Author Author: Jan Cumps
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PID temperature controller for the EasyL1105 MSPM0 board - Pt. 2: ADC

Jan Cumps
PID temperature controller for the EasyL1105 MSPM0 board - Pt. 2: ADC

  designed a development kit for the recent Texas Instruments MSPM0 microcontroller series. 
This 4 part blog series documents the steps to design a PID temperature controller. Part 2: add ADC to sample the temperature sensor

image
(post that introduces the kit)

Goal of this 2nd post

  • add single ADC conversion logic, based on TI adc12_single_conversion
  • use ADC hardware to return value in same Q16 format used in the PID library

Set up ADC SysConfig

image

The Conversion Data Format, 2s complement, left aligned, happens to be the same Q15 format that our PID library uses.

image

image

image

image

Code adaption from post 1:

I use a flag to check if sampling is done. The Result Loaded trigger will set that flag.

volatile bool gCheckADC;
uint32_t gAdcResult;

// ...

void ADC12_0_INST_IRQHandler(void) {
    switch (DL_ADC12_getPendingInterrupt(ADC12_0_INST)) {
        case DL_ADC12_IIDX_MEM0_RESULT_LOADED:
            gCheckADC = true;
            break;
        default:
            break;
    }
}

In main(), the IRQ gets enabled

int main(void) {
    SYSCFG_DL_init();

    // ...

    NVIC_EnableIRQ(ADC12_0_INST_INT_IRQN);
    gCheckADC = false;
    
    // ...

The perform_adc() placeholder that I wrote in the 1st post, gets implemented now:

void perform_adc() {
    DL_ADC12_startConversion(ADC12_0_INST);

    while (false == gCheckADC) {
        __WFE();
    }

    gAdcResult = (uint32_t)DL_ADC12_getMemResult(ADC12_0_INST, DL_ADC12_MEM_IDX_0);

    gCheckADC = false;
    DL_ADC12_enableConversions(ADC12_0_INST);
}

I could make gAdcResult a return value instead of a global variable. Maybe later ...

Thanks for reading. Next, get PWM working.

ccs project for EasyL1105: pid_EasyL1105_20250927.zip

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  • Made a bit more progress over the weekend.. still not attached the MOSFET circuit, but figured a little display could be useful. It's optional, the code will continue to run if it's missing of course.

    The photo shows the result, the screen is really small (0.85"), but on the plus side it's super-cheap ($2) and, since just a few digits are being displayed, the main values are visible from at least a couple of meters away.

    If anyone wants this exact screen, it is BuyDisplay ER-TFT0.85-1  and has 128x128 resolution. The supplied code wasn't ideal, but I've modified it slightly, and now it works fine with the MSPM0 chip (and can be used with any microcontroller supporting SPI). To keep ROM usage low I've only implemented Hershey font with ASCII characters " " to "Z", no lower-case text. (Font ROM usage is about 1600 bytes which is approx. 5% of total ROM, could be optimized further).

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        // tft test
    lcd_Initial();
    USE_HORIZONTAL=0;
    ClearScreen(0x0000);	// black

    drawText("ACTUAL DEG C", 5, 25, 0.5f, 0.8f, PEN_THIN, YELLOW);
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    drawText("SET: 250.0", 10, 125, 0.6f, 1.0f, PEN_THIN, CYAN);

    image

    Physically, these are the connections I made:

    GPIO   TFT_LABEL          EASYL1105_LABEL   MyWireCol
-----  ----------------   ---------------   ---------
PA4  : TFT_RESET          Labeled MISO      BLUE
PA6  : TFT_SCL (CLOCK)    Labeled SCK       YELLOW
PA5  : TFT_SDA (DATA)     Labeled MOSI      GREEN
PA3  : TFT_CS             Labeled CS1       PINK
PA24 : TFT_D/C            Labeled CS2       PURPLE
     : VDD                3.3V              RED
     : GND                GND               BLACK
       LED_A              3.3V via 10-ohm
       LED_K              GND               BLACK

    Also through implementing it, I discovered a bug with the MSPM0 Python programmer, it's now fixed on GitHub.

    The code I'm using is here:

    pid_EasyL1105_with_tft.zip

  • in reply to Jan Cumps

    I've added a simple CLI.

    It accepts lines with the syntax:

    <paramname> <value>

    or 

    <paramname>?

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    kp?

    To set it to a new value (e.g. 500):

    kp 500

    The CLI is quite generic, so it can be used for other MSPM0 programs (or any microcontroller).

    The uart.c code is responsible for filling uart_buffer as characters arrive, and setting a global variable uartLineReceived whenever a line of text has been typed.

    Commands are parsed and processed in cli.c / cli.h using a function called process_line.

    In the main() function, the following is used to call process_line:

    if (uartLineReceived) {
    process_line((char *)uart_buffer);
    uartLineReceived = false;
}

    I still need to connect up a potentiometer, and wire a MOSFET, I'll do that next.

    pid_EasyL1105_with_cli.zip