Advanced Micromouse
Hardware Design
Lecture Outline
 Microcontroller
 Power System
 Peripherals
 Sensor System: IR emitters and receivers
 Motor Controller
 Gyro
 Buzzer
 Display
 Voltage Meter
 LEDs
 Push Button
 Reset Button
Microcontroller
 STM32F405RGT6 – 64 pins
 Timers - Generate PWM signals to motor, buzzer
 GPIOs – LEDs, IR emitters, push button
 USART – Allows “printf” to display on a terminal
 SPI – Prints data on alphanumeric display
 ADC – Convert analog voltage to a digital number
 1 MB Flash – Store maze info
Microcontroller Pins
 Multi-function pins
Power System - Microcontroller
 Power Supply Schemes:
 VDD = 1.8 to 3.6 V: external power supply that will supply the
voltage for GPIOs (Futura Mouse: 3.3 V)
 VDDA = 1.8 to 3.6 V: external analog power supply for ADC, DAC,
Reset blocks, RCs and PLL (Futura Mouse: 3.3 V)
 VBAT = 1.65 to 3.6 V: power supply for RTC, external 32 kHz
oscillator, backup registers (Futura Mouse: 3.3 V)
 VSSA = GND for VDDA; VSS = GND for VDD
 VCAP: connect 2.2 microFarad ceramic cap between this pin and
GND (External capacitor that decouple power supply)
Power System
Power System – Power Supply
 Fully Charged Battery: 8.4 V (2 x 4.2 V)
 Motor Controller System (Level shifter + H-Bridge)
 5V regulator
 5V
 Encoders, IR Emitters (anode “+”), Alphanumeric Display
 3.3 V regulator
 3.3 V
 Microcontroller, Buzzer, USART, push buttons
 3.3 VA (analog circuits)
 IR Receivers, Gyro
8.4V Power - Battery
Power 5V
Power 3.3V and 3.3VA
IR Emitter - Front
(SFH4545)
IR Emitter – Diagonal
SFH4545
IR Receiver
(TEFT4300)
IR Sensor Pulsing Timing
Delay
between
each sensor
reading until
all residues
are gone
Motor Driver
Level Shifter
IC
H-Bridge IC
Gyro
Buzzer
- Buzzer behaves like an inductor
- Diode is used to prevent inductive
kickback
Display
Voltage Meter
Keep track of the battery
voltage to protect the
battery from over
discharging
LED
 2 ways to control LED with
MCU
 The one on left is easier for
wiring since ground is easier
to find
 The way to the right is
better in terms of power,
since power is not drawn
from the MCU
 Futura Mouse uses left
scheme
Push Button
-Futura Mouse uses right scheme
Boot0 Button
 For new MCUs,
Figure 1
Figure 2
bootloading
must be done
just once via
USART
 Boot mode must
be entered first
before
bootloading
 Figure 2 shows
how to save one
button
System memory boot mode
- Bootloader is stored in the system memory (ROM).
- To enter boot mode, set Boot0 high by holding down on the Boot0 push button,
then push the reset button. Boot1 should be connected to GND.
- Using USART, load application programs into FLASH.
Boot0 and Boot1
Reset Button
 Use Reset to reset the state of
the mouse, instead of the
power ON/OFF switch
 This button is IMPORTANT
for entering system memory
boot mode
 Reset is active low
References
 http://www.st.com/web/en/resource/technical/document/datasheet/DM00037051.pdf

STM32F405 MCU datasheet
 http://www.seattlerobotics.org/encoder/mar97/basics.html

Info about pull-up and pull-down resistors
 http://coactionos.com/embedded%20design%20tips/2013/10/21/Tips-UnderstandingMicrocontroller-Pin-Input-Output-Modes/

Info about pin input/output modes (i.e. push-pull, open-drain)
 http://www.allaboutcircuits.com/vol_3/chpt_3/9.html

Info about inductive kickback
 https://learn.sparkfun.com/tutorials/capacitors/application-examples

Info about decoupling capacitors (filters)
 http://learn.parallax.com/node/258

Info about phototransistor circuits (IR receiver)