EE345M Spring 2002 Quiz 2 Page 1 of 3 Jonathan W Valvano First Last April 10 2002 9 00 to 9 50 am This is an open book open notes exam You must put your answers on these pages only You can use the back You have 50 minutes so please allocate your time accordingly Please read the entire quiz before starting 30 Question 1 The following is a simple IIR digital filter y n 0 70x n 0 65x n 1 0 15x n 2 0 5y n 1 0 25y n 2 The unsigned 8 bit input data from A2D 0 is bounded between 0 and 255 You may assume the filter gain is less than one so the y n values are also bounded between 0 and 255 No floating point calculations are allowed For full credit you must implement the filter without approximation Be careful to specify whether you use 16 or 32 bit integer math Assume TMSK2 contains its initial value of 0 Specify the CONSTANT required for 1000 Hz sampling unsigned char x 3 y 3 8 bit unsigned numbers 0 to 255 pragma interrupt handler TC5Handler define CONSTANT fill in the value here to make fs equal to 1000Hz void TC5Handler void TFLG1 0x20 ack interrupt TC5 TC5 CONSTANT fs 1000Hz add code here to shift the MACQ x 0 A2D 0 new 8 bit data 0 to 255 add code here to execute the filter pragma abs address void OC5 vector TC5Handler pragma end abs address fill in the vector here EE345M Spring 2002 Quiz 2 Page 2 of 3 30 Question 2 Design an analog circuit that has the transfer function Vout 4 V1 10 V2 5 V1 and V2 are analog inputs and Vout is the analog output You do not need to worry about input or output impedance Your circuit will operate on a 12 V supply using REF02 references and OP07 op amp s The REF02 creates a 5 00 reference voltage Full credit will be given to proper solutions using one REF02 and one OP07 op amp Show the analog circuit Label all resistor values You do not need to show the power supply connections for the OP07 and REF02 EE345M Spring 2002 Quiz 2 Page 3 of 3 40 Question 3 In this problem you will design an instrument to measure weight using the Maxim MAX1247 The range of weight is 0 to 400 lbs Because you are using a 12 bit ADC and the system is linear the measurement precision will also be 12 bits The frequencies of interest are 0 to 1 Hz The weight is measured with 4 resistive strain gages placed in a bridge two in compression 100 R two in expansion 100 R The sensitivity of each gage is 0 005 lbs The change in transducer resistance R is linearly related to weight 10 Part a Complete the following table Data is the digital result from the unsigned 12 bit ADC The system will use the full scale 0 to 2 5V ADC range Refer to the circuit in part c Data W R R1 R2 R3 R4 V1 V2 V1 V2 V3 0 0 100 100 100 100 0 00 200 1 99 101 101 99 1 25 400 2 98 102 102 98 2 50 lbs V V V V 5 Part b What sampling rate would you choose Why 5 Part c Specify the desired gain for the instrumentation amp 5 00V R1 V 1 R2 Rf R3 R4 AD620 V3 Max1247 6812 SPI V2 5 Part d Specify the Rf resistor that implements that gain 5 Part e What is the maximum allowable noise of the analog circuit referred to its input at V1 V2 5 Part f What is the measurement resolution in lbs 5 Part g Floating point is not available The software will perform many mathematical calculations on the measurement What number format would you suggest be used to represent the weight Be as specific as possible