Transcript lab_autobalance
ECE243
LEGO Autobalance LAB 1
But first: LOGICAL SHIFTS
• SLL/SLLI: shift left logical – like ‘<<’ in C • SRL/SRLI: shift right logical – like ‘>>’ in C • NOTE: new bits shifted in are zeros • Ex: SLLI r8, r9, 0x4 • Ex: SRLI r8, r9, 0x3 2
Bit Fields and Masking
• Use a word, hword, or byte to hold multiple values – ex, packing ctrl & data signals into a connector (GPIO) – ex, packing small fields to save memory • Ex: Course info: – department: (ECE, CIV, etc) 12 total => – Course code: 0..2000
=> – Fall, spring: F, S => • Better than one halfword each: – 3 * 16 bits = 48bits 3
Course info Example
#put dept in r8: #Put course code in r8: #Put F/S in r8:
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Next Lab: You will Build a Segway!
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Actually, a LEGO Autobalancer
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LEGO Setup
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LEGO Controller
0xF means low light F 0 0x0 means full light 8
LEGO Breakout Box
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Autobalancer with Breakout Box
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Fixed Distance: Varying Distance:
Using Sensors
Sensor 0x0 (full light) Sensor 0x7 (some light) Sensor 0xF (low light) Sensor Sensor 0x0 (full light) 0xD (low light) 11
Talking to LEGO Controler via GPIO
• Bits0..9
– configure/control 5 motors – enable/disable; clockwise/counter-clockwise • Bits10..19
– configure/control 5 sensors • Bits27..30
– read data value from sensors • 2 ways to use sensors: – polling mode (default mode, recommended) – state mode (more advanced, see documentation) 12
Motor control
9 0(JP1): (DR): for/ rev 8 on/ off 7 for/ rev 6 on/ off 5 for/ rev 4 on/ off 3 for/ rev 2 on/ off 1 for/ rev 0 on/ off motor4 motor3 motor2 motor1 motor0 • for/rev: 0 = forwards/clockwise, 1 = reverse/ctr-clk-wise • on/off: 0 = on, 1 = off 9 8 7 6 5 4 3 2 1 0 4(JP1): (DIR) 1 1 1 1 1 1 1 1 1 1 motor4 motor3 motor2 motor1 • set to all 1’s, since they are all outputs motor0 13
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Sensor control
17 16 15 14 13 0(JP1): (DR) rdy? on/ off rdy? on/ off rdy? on/ off 12 rdy? on/ off 11 10 rdy? on/ off sensor4 sensor3 sensor2 sensor1 sensor0 • on/off: 0 = on, 1 = off • rdy (ready): 0 = ready/valid, 1 = not-ready/invalid 4(JP1): (DIR) 19 0 18 1 17 0 16 1 15 0 14 1 13 0 12 1 11 0 10 1 sensor4 sensor3 sensor2 • set to 1’s for on/off bits (outputs) • set to 0’s for ready bits (inputs) sensor1 sensor0 14
Sensor values
0(JP1): (DR) 30 29 28 27 Sensor value • 4-bit sensor value – can only read one sensor value at a time – first enable one sensor, then await ‘ready/valid’, then read 30 29 28 27 4(JP1): (DIR) 0 0 0 0 Sensor value • set direction for sensor value bits to 0’s • since they are inputs 15
Direction Register DIR
• Typical use of DIR: – set to 1(output): • bits0..9 (motor enables), bits10,12,14,16,18 (sensor enables) – set to 0 (input): • bits 11,13,15,17,19 (sensor readys), bits27..30 (sensor value) – Set to 0bxx00 00xx xxxx 0101 0101 0111 1111 1111 – X’s must also be set to certain values (see docs) • Magic number for typical use: (set DIR to this) – 0b0000 0111 1111 0101 0101 0111 1111 1111 – 0x07f557ff 16
Ex: enable motor1, forward .equ ADDR_JP1, 0x10000060 movia r8,ADDR_JP1 movia r9, 0x07f557ff # set DIR to typical-use value stwio r9, 4(r8) movia r9, 0xfffffff3 stwio r9,0(r8) # 0b... 11110011 # bit2=0 for enabled, bit3=0 for forward 17
Ex: read sensor2
.equ ADDR_JP1, 0x10000060 movia r8,ADDR_JP1 movia r9, 0x07f557ff # set DIR to typical-use value stwio r9, 4(r8) movia r9, 0xffffbfff # bit14=0 to enable sensor2 stwio r9,0(r8) POLL ldwio r9,0(r8) # read DR srli r10,r9,15 # shift bit-15 to the bit-0 position andi r10,r10,0x1 # mask it to isolate it bne r10,r0,POLL # ready if r10==0, try again otherwise srli r9,r9,27 # shift-right-logical-immed by 27 bits # sensor value is now in lowest 4 bits of r9 andi r9,r9,0x0000000f # mask it to isolate it # can now use sensor value in r9 18
Some Hints
• Do not use delay counters, must use timer • Not all sensors are equal – sensitivities vary, you must calibrate them • motors will stall if you switch directions fast • motors can be too fast/jerky: – if you give it full voltage: – instead give it part voltage: – called Pulse Width Modulation (PWM) • See DESL for full details!
– page on Lego Controller (quick reference) – full Lego manual (pdf) 19