ECE2049: Embedded Computing in Engineering Design C Term Spring 2018 Lecture #15: More ADC Examples

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1 ECE2049: Embedded Computing in Engineering Design C Term Spring 2018 Lecture #15: More ADC Examples Reading for Today: TI example code Reading for Next Class: Users Guide 6.2, Davies Ch HW #4 (on web): Due MONDAY 2/12 (in class) Lab #2 (on web): Bonus sign-off 2/9. Report due TUE 2/13 (in class) Exam #2 TUESDAY 2/13/2018 at 9 am in AK-116 Last Class: Basic settings for the ADC12 registers for a simple single channel, single conversion measurement >> Use code examples >> Add new requirements as needed starting from working code Let's stand back and take stock... >> All of the interfacing to and programming of peripherals is just IO! --> In general purpose computing this is automagically handled by OS... but the embedded systems programmer has to implement it all A Key Part is using code examples to help figure out those peripheral control registers! >> Last class we set up the ADC12 for to take a single measurement from our example current measurement circuit This involved specific settings for ADC12CTL0, ADC12CTL1 and ADC12MCTL0 registers MSP430F5529 Analog-to-Digital Converter (ADC12_A) 16 channel, 12-bit sample and hold ADC (200k samples per second max) 12 External Analog Inputs A0-A7, A12-15 use same pins as Ports 6 & 7 4 internal Analog Inputs A8-A11 Configure and use by setting values in various control registers ADC12CTL0 controls the following options (BOLD = we'll need to set) -- Sample and Hold time (ADC12SHT1x and ADC12SHT0x) -- Multiple sample conversion method (ADC12MSC) -- Reference Voltages (ADC12REF2_5V and ADC12REF_ON) -- ADC12ON bit -- Enable and start conversion (ADC12ENC and ADC12SC) -- Overflow/Conversion time int. enables (ADC120VIE, ADC12TVIE)

2 ADC12CTL1 controls the following options -- Conversion start address (ADC12CSTARTADDx ) -- Sample and hold source select (ADC12SHSx) -- Sample and Hold pulse mode selectable (ADC12SHP) -- Invert signal sample and hold (ADC12ISSH) -- ADC12 clock divider (ADC12DIVx) -- ADC12 clock source select(adc12sselx) -- Conversion mode select (ADC12CONSEQx) -- ADC12 busy/conversion not complete bit (ADC12BSY) >> Results from each channel are stored in the low 12 bits of one of 16 Conversion Memory Registers (ADC12MEMx) x x x x d 11 d 10 d 9 d 8 d 7 d 6 d 5 d 4 d 3 d 2 d 1 d 0 >> Each memory register has a corresponding Conversion Memory Control Register (ADC12MCTLx) Each ADC12MCTLx controls the following options for its Memory Register -- **End of Sequence (EOS) = Is this channel the end on a sequence of channels that are to be converted. Needed when converting a sequence of channel** -- Select Reference Voltages (ADC12SREFx) = We'll use ADC12SREF_0 = Vcc and GND or ADC12SREF_1 = Internal Vref+ (either 2.5V or 1.5V) and GND -- Analog input channel selection (ADC12INCHx) = ADC12INCH_0 to ADC12INCH_15 So what does the programmer need to do to use ADC12_A? 1) Select ADC Core Behavior: Using ADC12CTL0 and ADC12CTL1 registers -- Set Clock Source (4 options) and Divider (8 options) We use defaults: ADC12SSELx = 00 = ADC clock ADC12OSC (~5 MHz) ADC12DIVx = 000= divide ADC12CLK by 1 -- Set Sample & Hold behavior Here we'll use a middle of the road setting ADC12SHT0x = ADC12SHT0_9 = 1001b = 9h (384 clk cycles)

3 -- Reference Voltages = This will depend on Application!! (Must clear REFMSTR bit to use internal ref voltages: REFCTL0 &= ~REFMSTR;) --> Turn on Internal Reference Voltages: ADCREFON = 1 --> Select V ref+ as 1.5V or 2.5V: ADC12REF2_5V = 1 (2.5V), = 0 (1.5V) 2) Select Conversion Mode required: ADC12CONSEQx bits in ADC12CTL1 reg -- Single channel or a sequence of channels -- Also single conversion or repeated conversions 3) Select input channel(s): ADC12INCHx bits in ADCMCTLx registers >> ADC12 has 12 (external) analog input signals and 4 internal inputs --> **ADC12's External Analog Inputs A0 A7 and A12-A15 are multiplexed with Port 6 and 7 pins so MUST set PxSEL register! IMPORTANT: Assume input channels A6 and A7 are to be used with ADC12_A. The Port Selection bits for those pins should be set to 1 = Function Select. A6 and A7 are multiplex with digital IO pins P6.6 and P6.7. P6SEL = (BIT6 BIT7); // Set pins to function mode (not IO!) >> Internal input channels 8, 9 & 11 (ADC12INCHx = 1000, 1001, 1011) are connected to different chip reference voltages Could be used to do health monitoring >> Internal input channel 10 (ADC12INCH_10 = 1010b) is connected to an internal Temperature Sensor (WE WILL USE IN LAB 3). 4) Enable appropriate interrupts -- ADC12IE register -- Do not have to use interrupts, but useful for repeated measurements -- Write ISR (should handle all possible ADC interrupts with some default behavior... a switch statement) 5) Enable and Start Conversion(s) -- ADC1CTL0 register //Enable and start (single) conversion (not using ADC int) ADC12CTL0 = ADC12SC + ADC12ENC;

4 // Some code to implement the current sensor example from last // class. Input voltage range 0 to 2.5V corresponds to 0 to 1A. unsigned int in_value; // Reset REFMSTR to hand over control of internal reference // voltages to ADC12_A control registers REFCTL0 &= ~REFMSTR; // Initialize control register ADC12CTL0 = // SHT0x = 9h (384 clk cycles), MCS = 0 = no burst mode // REF2_5V = 1 (2.5V), REFON = 1 = use internal reference volt // and ADC12ON = 1 = turn ADC on ADC12CTL0 = ADC12SHT0_9 ADC12REFON ADC12REF2_5V ADC12ON; // Initialize control register ADC12CTL1 = // ADC12CSTART ADDx = 0000 = start conversion with ADC12MEM0, // ADC12SHSx = 00 = use SW conversion trigger, ADC12SC bits // ADC12SHP = 1 = SAMPCON signal sourced from sampling timer, // ADC12ISSH = 0 = sample input signal not inverted, // ADC12DIVx = 000= divide ADC12CLK by 1, // ADC12SSEL=00= ADC clock ADC12OSC (~5 MHz), // ADC12CONSEQx = 00 single channel, single conversion, // ADC12BUSY = 0 = no ADC operation active ADC12CTL1 = ADC12SHP; // Set conversion mem control register ADC12MCTL0 = // EOS = 0, SREF =001 -->Voltage refs = GND to (Vref+) // INCHx = 0000 = analog input from A0 ADC12MCTL0 = ADC12SREF_1 + ADC12INCH_0; P6SEL = BIT0; // Set Port 6 Pin 0 to FUNCTION mode for ADC ADC12CTL0 &= ~ADC12SC; // clear the start bit //Enable and start (single) conversion (not using ADC int) ADC12CTL0 = ADC12SC + ADC12ENC; // Poll busy bit waiting for conversion to complete while (ADC12CTL1 & ADC12BUSY) no_operation(); in_value = ADC12MEM0 & 0x0FFF; // keep only low 12 bits >>Now what do we do with in_value?

5 Ex: Starting with the code from that example how should we configure the ADC12 registers to take a single measurement from the Internal Temperature Sensor.

6 #include <msp430.h> // Temperature Sensor Calibration Reading at 30 deg C is stored // at addr 1A1Ah. See end of datasheet for TLV table mapping #define CALADC12_15V_30C *((unsigned int *)0x1A1A) // Temperature Sensor Calibration Reading at 85 deg C is stored // at addr 1A1Ch See device datasheet for TLV table mapping #define CALADC12_15V_85C *((unsigned int *)0x1A1C) unsigned int in_temp; int main(void) { volatile float temperaturedegc, temperaturedegf, degc_per_bit; WDTCTL = WDTPW + WDTHOLD; // Stop WDT degc_per_bit = ((float)( ))/ ((float)(caladc12_15v_85c-caladc12_15v_30c)); // Reset REFMSTR to hand over control of internal reference // voltages to ADC12_A control registers REFCTL0 &= ~REFMSTR; // Internal ref is on and set to 1.5V ADC12CTL0 = ADC12SHT0_9 ADC12REFON ADC12ON; ADC12CTL1 = ADC12SHP; // Enable sample timer ADC12MCTL0 = ADC12SREF_1 + ADC12INCH_10; delay_cycles(100); // delay to allow Ref to settle ADC12CTL0 = ADC12ENC; // Enable conversion while(1) { ADC12CTL0 &= ~ADC12SC; ADC12CTL0 = ADC12SC; // clear the start bit // Sampling and conversion start // Single conversion (single channel) // Poll busy bit waiting for conversion to complete while (ADC12CTL1 & ADC12BUSY) no_operation(); in_temp = ADC12MEM0; // Read results from conversion temperaturedegc=(float)(((long)in_temp-caladc12_15v_30c) *degc_per_bit ; // Temperature in Fahrenheit = (9/5)*Tc + 32 temperaturedegf = temperaturedegc * 9.0/ ; } } no_operation(); // SET BREAKPOINT HERE

7 Ex: Now, what if you wanted to monitor both the current through the sensing resistor and the internal temperature of the chip at the same time? How should we set up the ADC registers to do that? >> This is a multiple channel, single conversion problem >> What setting are changed from the single channel problem?

8 #define MA_PER_BIT // =1.0A/4096 // Temperature Sensor Calibration readings for 2.5V from TLV #define CALADC12_25V_30C *((unsigned int *)0x1A22) #define CALADC12_25V_85C *((unsigned int *)0x1A24) unsigned int in_current,in_temp; float milliamps, tempc; // Reset REFMSTR to hand over control of internal reference // voltages to ADC12_A control registers REFCTL0 &= ~REFMSTR; // Initialize control register ADC12CTL0 = // SHT0x=9h (384 clk cycles), MCS=1=burst thru selected chans., // REF2_5V = 1 (2.5V), REFON = 1 = use internal reference volts // and ADC12ON = 1 = turn ADC on ADC12CTL0=ADC12SHT0_9 ADC12REFON ADC12REF2_5V ADC12ON ADC12MSC; // Initialize control register ADC12CTL1 = // ADC12CSTART ADDx = 0000 = start conversion with ADC12MEM0, // ADC12SHSx = 00 = use SW conversion trigger, ADC12SC bits // ADC12SHP = 1 = SAMPCON signal sourced from sampling timer, // ADC12ISSH = 0 = sample input signal not inverted, // ADC12DIVx = 000= divide ADC12CLK by 1, // ADC12SSEL=00= ADC clock ADC12OSC (~5 MHz), // ADC12CONSEQx = 01 = sequence of channels converted once // ADC12BUSY = 0 = no ADC operation active ADC12CTL1 = ADC12SHP+ADC12CONSEQ_1; // Set conversion memory control registers for the 2 channels // ADC12MCTL0: EOS = 0, SREF =001 = voltage refs = GND to Vref+ // INCHx = 0000 ADC12MCTL0 = ADC12SREF_1 + ADC12INCH_0; // ADC12MCTL1: EOS = 1, SREF =001 = voltage refs = GND to Vref+ // INCHx = 1010 ADC12MCTL1 = ADC12SREF_1 + ADC12INCH_10 + ADC12EOS; // Set Port 6 Pins 0 to FUNCTION mode (=1) for ADC12 P6SEL = P6SEL BIT0; // Forever loop to take measurements while (1) { //Enable and start single burst conversion ADC12CTL0 = ADC12SC + ADC12ENC; while (ADC12CTL1 & ADC12BUSY) // poll busy bit no_operation(); in_current = ADC12MEM0 & 0x0FFF; // keep only low 12 bits in_temp = ADC12MEM1 & 0x0FFF; // keep only low 12 bits } milliamps = (float)in_current * MA_PER_BIT; tempc = (float)(((long)in_temp-caladc12_25v_30c)*(85-30))/ (CALADC12_25V_85C - CALADC12_25V_30C) ;