ECE2049 Homework #4 Analog-to-Digital Conversion and the ADC12 (Due Thursday 2/15/2018 to box outside AK-011 by 9 am)

Transcription

1 ECE2049 Homework #4 Analog-to-Digital Conversion and the ADC12 (Due Thursday 2/15/2018 to box outside AK-011 by 9 am) PLEASE (NEATLY) SHOW ALL WORK! Comment all code well. Do not make the grader guess what your doing! All code should be typed. To ensure proper grading & return, you must attach the included cover sheet! Refererence: Davies Ch 9.2-3, 9.7, MSP430x55xx User's Guide Ch. 28, class notes, examples, TI code examples 1) With the ADC12_A as configured below, for each analog input list the specific values of the following given that the external reference voltage V eref+ = 2.2V (15 pts) i. Full-scale range, ii. Resolution, iii. Dynamic Range iv. Input Channel v. Memory output register unsigned int value, VV, in;... REFCTL0 &= ~REFMSTR; ADC12CTL0 = ADC12SHT0_10 + ADC12SHT1_10 + ADC12REFON + ADC12REF2_5V + ADC12ON + ADC12MSC; ADC12CTL1 = ADC12CSTARTADD_5 + ADC12SHP; P6SEL = BIT3; P7SEL = BIT0; ADC12MCTL5 = ADC12SREF_0 + ADC12INCH_3; ADC12MCTL6 = ADC12SREF_2 + ADC12INCH_12; ADC12MCTL10 = ADC12SREF_1 + ADC12INCH_11 + ADC12EOS; ADC12CTL0 = (ADC12SC ADC12ENC); while (ADC12CTL1 & ADC12BUSY) no_operation(); value = ADC12MEM5 & 0x0FFF; in = ADC12MEM6 & 0x0FFF; VV = ADC12MEM10 & 0x0FFF;

2 b. What is the code value in VV for the default voltage on that input channel? What is the voltage value on the corresponding analog input if value = 0x0640? What is the code value in in if the voltage on the corresponding input is 0.85V? (5 pts) 2) A certain pressure sensor has a sensitivity of 1.08 mv/kpa (kilopascal). The analog output of this pressure sensor is to be connected to the input of an external analog-todigital converter. Atmospheric pressure at sea level is approximately 14.7 psi which is equal to 1 atmosphere (1atm) and 1.0 KPa = psi.. (30 pts) a. The pressure sensor's data sheet lists its analog output range as 0 2.0V. What is the minimum number of bits that the ADC must have to be able to detect changes of 0.21kPa? (Do not assume that you must use the MSP430's built-in 12-bit ADC). b. What is the dynamic range of the ADC from part (a). c. What is the pressure in kpa associated with the full-scale reading of 2.0V if the minimum detectable pressure is actually 0.12 kpa (i.e. 0V corresponds to 0.12 kpa rather than a perfect vacuum, 0 kpa)? d. What is the dynamic range of the pressure sensor in db? e. Assume that the output of the ADC from part (a) has been read into the global variable unsigned int adcpressure. Write a C function that converts adcpressure to atmospheres. f. If adcpressure=0x060e, what is the pressure in kpa and in atmospheres. 3) Accelerometers measure the force of gravity. A particular accelerometer has a range of g but is currently being used simply as a single axis tilt sensor as shown below. The analog output voltage of the accelerometer is 1.2V at 0 g and the device has a sensitivity of 399 mv per g. Assume the output of the accelerometer is input into the MSP430's 12- bit analog to digital converter, and that the ADC12_A is configured using the code shown below. (30 pts) Accelerometer orientation and readings for 4 different tilt values: Tilt = 0 o Tilt =45 o Tilt = 90 o Tilt = 180 o Reads 1 g Reads g Reads 0 g Reads -1 g

3 a) What is the Full Scale Range of the accelerometer in g's? What is the FSR of the ADC12 in volts as it is configured above? b) Given the settings in the code above, what is the resolution (in volts/bit) of ADC12_A? c) What is the output of the ADC12 in hex for tilt readings of 0 o, 45 o, 90 o and 180 o. d) Given the information and the diagram above, write the C function calc_tilt() that converts the ADC12 output in adc_tilt to a tilt angle from 0 to 180 degrees. You may assume the C math library <math.h> is available. Code must be typed to be graded. e) Can your tilt measurement system detect a 1 degree tilt from horizontal (0 o to 1 o )? What is the smallest tilt (in degrees) from horizontal that you can measure? void tiltmeter() { unsigned int adc_tilt; P6SEL = BIT1; ADC12CTL0 = ADC12SHT0_9 ADC12REFON ADC12ON; ADC12CTL1 = SHP; ADC12MCTL0 = SREF_0 + INCH_2; //Enable and start (a single) conversion ADC12CTL0 = (ADC12SC ADC12ENC); while (ADC12CTL1 & ADC12BUSY) no_operation(); adc_tilt = ADC12MEM0 & 0x0FFF; } calc_tilt(adc_tilt);... 4) An MSP430 is being used to monitor the temperature inside 3 different experimental chambers over time. Using the code examples from class and the TI website as a guide, write a code segment in C that uses the ADC12 to sample the temperature inside each of the experimental chambers 10 times per second. Your code should configure the timer and the ADC, make the conversions and express the results in degrees C. You do not have to convert the results to ASCII for display. The output from the thermistors for Chambers 1 through 3 are connected to analog inputs A2, A3, A7 respectively. The thermistors inside the chambers are linear across the temperature range of interest (-45C o to 80C o ) with Vtemp = *(Temp C o ) V.

4 What temperature corresponds to an ADC measurement of 0x04FA for you temperature monitoring system? What ADC measurement corresponds to -4 C o? Code must be typed to be graded.(30 pts) You must document the following in your solution -- What input channels (ADC12INCHx) are used, What memory conversion registers are used, Are you using single channel or sequential channel mode, Continuous or one-shot conversion. Also list you choice for the reference voltage V ref. You may use code similar to the TimerA2 stop watch example to measure time. You do not have to use ADC12_A interrupts but you may. As is often the case, there are multiple approaches to this problem. Remember to TYPE ALL CODE!

5 ECE2049 Homework #4 Submitted by: ECE Box #: Date: Question Grade Total: