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2007: Q6 A student has decided to use a µC for a steady hand game. His system diagram is below µC LED 1 (life 1) Output 0 LED 2 (life 2) Output 1 Wand & Contacts Input1 LED 3 (life 3) Output 2 Transducer driver Buzzer Output 3

Requirements A:Each time the wand & track touch, the µC switches on & an LED in sequence 1, 2 & 3. Once an LED is lit it will stays lit until reset (9 marks) B: once the wand & track touch, the µC will ignore any further contact between the wand & track for 2 seconds (4 marks) C: On the loss of the third life, the buzzer will switch on for 0.25s, then switch off for 0.25s. This is repeated 3 times (6 marks) The µC will then reset back to “no lives lost” (3 marks) Total: 22 marks

START 2007 ELECTRONIC PRODUCTS Requirement ‘A’ Sample answer 9 marks Has Wand made contact NO YES Output 0 = 1 Has Wand made contact NO YES Output 1 = 1 Has Wand made contact NO YES Output 1 = 1 END

START 2007 ELECTRONIC PRODUCTS Requirement ‘B’ Sample answer Additonal 4 marks WAND ? NO YES WAIT 2S OUTPUT0=1 WAND ? NO YES WAIT 2S OUTPUT0=1 WAND ? NO YES WAIT 2S OUTPUT0=1 END

2007 ELECTRONIC PRODUCTS START Requirement ‘C’ Sample answer Additional 6 marks START WAND ? NO SUB0 YES WAIT 2S COUNT=1 OUTPUT0=1 OUTPUT3=1 WAND ? NO WAIT 0.25 YES WAIT 2S OUTPUT3=0 OUTPUT0=1 WAIT 0.25 WAND ? NO COUNT=3 YES RETURN YES NO WAIT 2S COUNT= COUNT + 1 OUTPUT0=1 SUB 0 END

2007 ELECTRONIC PRODUCTS START Requirement ‘D’ Sample answer Additional 3 marks START WAND ? NO SUB0 YES WAIT 2S COUNT=1 OUTPUT0=1 OUTPUT3=1 WAND ? NO WAIT 0.25 YES WAIT 2S OUTPUT3=0 OUTPUT0=1 WAIT 0.25 WAND ? NO COUNT=3 YES RETURN YES NO WAIT 2S COUNT= COUNT + 1 OUTPUT0=1 SUB 0 ALL OUTPUTS=0