CPE/EE 323 Introduction to Embedded Computer Systems Homework V

Transcription

1 CPE/EE 323 Introduction to Embedded Computer Systems Homework V 1(15) 2(15) 3(25) 4(25) 5(20) Total Problem #1 (15 points) Power, Low power systems A sensor platform features a microcontroller, a sensor, and a wireless radio interface. Your application operates with system frequency of 50 Hz, repeating the following sequence. The microcontroller samples an analog signal from the sensor, process the samples, and send the data to the radio chip. The radio then transmits the data to the network coordinator. After the data are sent wirelessly, the system goes into a sleep mode (the sensor, the microcontroller, and radio chip are all in low power mode). Assume that all devices wake up in the active mode when the time comes for the next application cycle, and stay active until the whole application cycle is completed. The radio chip is in the receive mode unless it transmits the data. From corresponding reference manuals we extracted information about the current drawn by each device when it is in active mode and when it is the low-power mode. Device Active mode I [ma] current Low-power mode I -- current Sensor ua Microcontroller 5 50 ua Radio transmit ua Radio receive ua By performing performance profiling of our application we found the following execution times: Type of operation Execution Time Sample sensor signals 0.2 ms Process samples 2 ms Send data to radio 1.8 ms Radio transmission 2 ms A. (10 points) Calculate the total execution time and the total sleep time during one application cycle. Calculate the average current drawn by the platform while in the active mode (IAM) and in the low-power mode (ILPM). Calculate the total average current drawn by the platform ITOTAL. B. (5 points) Calculate the total power P consumed (in milliwatts) if we power the platform by two AA batteries (Vsupply = 3.0 V). Determine the system operating time in days if we know that the battery capacity is 2400mAh. How would you further reduce the power consumption and consequently extend the operating time of the given system? Explain.

2 Problem #5. (15 points). ADC, DAC A (2.5 points). A sensor device gives an analog voltage that is directly proportional to atmospheric pressure. The sensor output voltage is always in the range of 0.5 V (min) to 1.5 V (max). How would you configure the MSP430 s ADC12 to perform analog-to-digital conversion with maximum resolution? What is the digital value that corresponds to 1.25 V input voltage? Explain. B (2.5 points). What is the analog voltage at the output of the MSP430 s DAC if we use 2.5 V reference voltage and 9-bit resolution? The data register DAC12_DATA = 0x007A. C (10 points). Analyze the following code. Add missing comments in the code below. What does this program do? ACLK = 32kHz, MCLK = SMCLK = default DCO Hz, ADC12CLK = ADC12OSC MSP430xG461x XIN - Vin0 --> P6.0/A0 32kHz Vin1 --> P6.1/A1 XOUT - Vin2 --> P6.2/A2 Vin3 --> P6.3/A3 ****************************************************************************** #include "msp430xg46x.h" volatile unsigned int A0results[8]; volatile unsigned int A1results[8]; volatile unsigned int A2results[8]; volatile unsigned int A3results[8]; unsigned int Index; void main(void) WDTCTL = WDTPW + WDTHOLD; P6SEL = 0x0f; ADC12CTL0 = SHT0_8 + MSC + ADC12ON; ADC12CTL1 = SHP + CONSEQ_3; ADC12IE = 0x08; ADC12MCTL0 = INCH_0; ADC12MCTL1 = INCH_1; ADC12MCTL2 = INCH_2; ADC12MCTL3 = EOS + INCH_3; while (1) ADC12CTL0 = ENC; ADC12CTL0 = ADC12SC; bis_sr_register(lpm0_bits + GIE); LPM0 Stop watchdog Enable A/D inputs #pragma vector = ADC12_VECTOR interrupt void ADC12_ISR(void) A0results[Index] = ADC12MEM0; A1results[Index] = ADC12MEM1; A2results[Index] = ADC12MEM2; A3results[Index] = ADC12MEM3; Index = (Index + 1) & 0x7; no_operation(); SET BREAKPOINT HERE bic_sr_register_on_exit(lpm0_bits); Exit LPM0

3 Problem #3 (25 points) DMA Controller A (5 points). Sketch a block diagram illustrating main registers for a single channel in the MSP430. For each register describe its purpose and the initialization process. Circle the correct answer for the following questions. B (2 points) The DMA controller allows to: (i) Move data from one location to another without CPU intervention (ii) Increase the throughput of peripheral modules (iii) Reduce system power consumption (CPU in low power mode) (iv) All of above C (2 points) The upper byte of a byte-to-word transfer: (i) Remains with the previous value (ii) Is cleared (iii) Is loaded with the same values as the lower byte (iv) None of above D (2 points) When the DMA transfer mode DMAxTSELx = 1 is selected: (i) Each transfer requires a trigger (ii) A complete block is transferred with one trigger (iii) CPU activity is interleaved with a block transfer (iv) None of above E (2 points). NMI interrupts interrupt the DMA controller when: (i) GIE bit is set (ii) DMAIE is set (iii) ENNMI bit is set (iv) DMAEN is set F (2 points). The DMA destination address when the DMADSTBYTE = 1 and DMDSTINCRx = 3: (i) Remains unchanged (ii) Increments by one (iii) Decrements by two (iv) Increments by two

4 G (10 points). Analyze the following code. Add missing comments in the program. What does this program do? ACLK = UCLK 32768Hz, MCLK = SMCLK = default DCO Hz Baud rate divider with 32768hz = 32768Hz/9600 = 3.41 (000Dh 4Ah) MSP430xG461x / \ XIN Hz -- RST XOUT - P > "Hello World" N1 ****************************************************************************** #include "msp430xg46x.h" const char String1[13] = "\nhello World"; void main(void) WDTCTL = WDT_ADLY_1000; IE1 = WDTIE; P4SEL = 0x03; ME2 = UTXE1 + URXE1; UCTL1 = CHAR; UTCTL1 = SSEL0; UBR01 = 0x03; UBR11 = 0x00; UMCTL1 = 0x04A; UCTL1 &= ~SWRST; DMACTL0 = DMA0TSEL_10; DMA0SA = (int)string1; DMA0DA = TXBUF1_; DMA0SZ = 0014; WDT 1000ms, ACLK, interval timer Enable WDT interrupt P4.0,1 = USART1 TXD/RXD DMA0CTL = DMASRCINCR_3 + DMASBDB + DMALEVEL; bis_sr_register(lpm3_bits + GIE); Enter LPM3 w/ interrupts #pragma vector = WDT_VECTOR interrupt void WDT_ISR(void) DMA0CTL = DMAEN;

5 Problem #4 (25 points) Communication A (5 points). What is synchronous and asynchronous serial communication? Give an example for each, and sketch the block diagram to illustrate main connections between the transmitter and receiver. B (10 points). Your task is to initialize the USART0 device to carry out asynchronous serial communication with 9600 bit/sec using Hz as the source clock. Assume that we use 8-bit characters with a parity bit, and 2 stop bits. Will this communication work properly without modulation? How do you determine value in the modulation register? Use illustrations to support your answer including timing waveforms.

6 C (10 points). Illustrate the USART operation in SPI mode. Sketch the master, slave(s), and relevant registers in each module. Explain the sequence of steps in typical communication scenarios.

7 Problem #5 (20 points) LCD Display A (10 points). Light number 7 on the LCD in the static mode. Illustrate waveforms on relevant segment lines and common lines. How many writes into the LCD memory is required to display number 7 on the LCD?

8 B (10 points). Light number 7 on the LCD in the 4-mux mode. Illustrate waveforms on relevant segment lines and common lines. How many writes into the LCD memory is required to display number 7 on the LCD?