Transcript Outputting a control signal from a 'real' processor. What

Getting the O in I/O to work
on a typical microcontroller
Ideas of how to send output signals
to the radio controlled car.
The theory behind the LED controller
used in Assignment 1 and the Familiarization Lab
Agenda
• Processors need to send out control
signals (high / low 1 / 0 true / false)
– General Purpose Input / Output lines
(GPIO lines) on Blackfin chip (16)
– FLASH memory chip has additional I/O
ports connected to Ez-Lite KIT LED’s
• What do we need to have happen to
make the FLASH memory work on a
microcontroller as we want. (In this
example turning the board LED’s on and off)
• What new Blackfin assembly
language instructions do we need to
learn in order to operate the LEDs?
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Radio controlled car
In principle we could
• Connect the signal that controls the LED1
output directly to the turn-to-right signal
line of radio transmitter
• Connect the signal that controls the LED2
directly up to the go-forward signal line of
radio transmitter
• Connect LED3 control up to the turn-to-left
signal line of radio transmitter
• “IN PRINCIPLE” means – we might start off this way while
we initially explore ideas to control the car.
However we may (or may not) finish the project a different
way. COULD USE LEDs AS A VIRTUAL CAR CONTROLLER
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Programmable Flags (input Lab)
• Most micro-controllers have general
purpose input or output lines capable
of generating “true” or “false” values
• Blackfin 533 has 16 GPIO lines
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Where are the GPIO pins found on
the board? (Shared with video PPI controller)
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GPIO lines are very useful
• They are used to sent control signals
to many of the peripherals that are
found on the Blackfin Evaluation
Board.
– Video Control – GPIO PF0 to PF7
– Audio Control -- ?? (Never looked)
– Input -- Buttons – GPIO PF8, 9, 10, 11
– Output – GPIO PF0, PF1, PF5, PF6, PF7
– SPI interface control for LCD -- PF5
– SPI interface Haptic Control – PF6
– Pins are functionally multiplexed –
MEANS pins can perform different
functions at different times.
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Additional I/O pins available
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Used to control LED on board
• Controlled using special “additional”
parallel port interface attached to
“flash” memory chip
PROJECT USE
LEDs used to INDICATE
direction radio-controlled
car will move. Not
currently used to control
the car (but could).
LEFT
RIGHT
FORWARD
BACK
CONTROL ON
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FLASH MEMORY UNIT
• Major task of this unit is to store the code
need to “boot” (start) the processor
2 PSD4256G6V
From STMicroElectronics
The FLASH part we
need during Lab. 1
Additional I/O pins
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LEDs connected to FLASH port
BACK
FORWARD
RIGHT
LEFT
These pins are
controlling
other things
on the board
DON’T
CHANGE
PB6_A, PB7_A
BEHAVIOUR
WHEN YOU
CODE THE
LED
OPERATION
(Use AND / OR
instructions)
Blackfin BF533 I/O
Airplane falls from
sky syndrome
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Steps to activating LEDs
1. Get the FLASH memory to work
correctly (set many FLASH registers)
– Write the code for InitFlashASM( )
2. Get the FLASH I/O Port to work
correctly as output for pins PB5 
PB0, leaving other pins unchanged
– Write the code for InitFlashPortASM( )
3. Write the value we want to LEDs
– WriteFlashLEDASM( int value)
4. Read back the value the LEDs show
– int ReadFlashLEDASM( ) for testing
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FLASH MEMORY UNIT
• Controlled through “EBIU”
External Bus Interface Unit
EBIU are common on most processors (although often by different name)
FLASH
OTHER
PINS
USED
WAIL!
SDRAM
CONTROLLER
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Key information about EBIU
• Three busses come into the EBIU from
the Blackfin processor core
• Forwards data to SDRAM and FLASH
– How does EBIU “know” whether data has to be send to
FLASH unit (I/O)and which data to the SDRAM units (memory
store)????? (Control logic question on quiz / exams)
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SDRAM and FLASH
• In later laboratories
– We will build a stand-alone microcontroller system,
which means we will need to understand how to
program the flash memory so that the processor
“knows” what to do when powered-up.
Common practice on processors for boot process
reads start up code from FLASH
– We will need to process “large arrays” – too large
to fit into the “internal fast” Blackfin “L1” memory
so they must be placed in SDRAM.
Common practice on processors
• In this laboratory, we need to program the “extra”
FLASH chip I/O pins which are connected to the
LED’s – control the lights now, perhaps control car
later.
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What we know!
• When the processor powers up – it
must read its “boot” program from
the FLASH memory
• The processor does not know what
sort of FLASH it will be connected to
• When processor powers up, it will
“assume” that it is connected to
“slowest FLASH” in existence.
• The first part of the program the
processor reads in (boot code) can
change the processor to read FLASH
more efficiently (faster).
(common practice)
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Controlling FLASH operation
What
we
need
to
worry
about
Blackfin (like most microcontroller peripherals) has a “GLOBAL”
control register and one or more “specific” control registers
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InitFlashCPP( )
• Get the FLASH memory to work correctly
• May be “many” processes (threads) running on the
Blackfin evaluation board (e.g. Audio).
• All these processes (threads) may want to use the
flash memory for other purposes – meaning
InitFlashCPP( ) may have already been called by
another thread before your code uses it (or perhaps
your code is run more than once)
•
InitFlashCPP( ) { /* Concept only */
If FLASH memory already configured -- ¿How can we know this?
-- Perhaps something that changes during initialization!
– return without changing the initialization
Else {
configure Memory Bank control register
THEN configure Global control
(turns on the FLASH)
}
}
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Set the Bank control register
• Reset value – the way the processor powers up
• Will probably work “as is” but not efficient – “slow
reads” by default (common practice for hardware)
Default
Slow (15
cycles for
each read
and write
operation)
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Memory control access speed (default
slow) – Diagram often appears in quiz
DEFAULT
Processor
sends out
address
and waits
15 cycles
before
sending a
“do a read
operation”
command
to memory.
The
processor
waits
another 15
cycles
before the
actual read
occurs.
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Set General Control Register
• Reset value (Processor power up state)
leaves “CLKOUT” disabled – is that important?
(Meaning do WE have to turn it on (set bit 0 to 1)?)
What parts of the operation of this
register must we “know” how to do?
Unanswered at this time. We don’t know
what bits are critical NOT to change. SO
CHANGE USING AND and OR instructions
when setting All Banks enabled
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• Get the Port to work correctly as
output for pins PB5  PB0, leaving
other pin behaviour (6 and 7)
unchanged. (Use AND and OR
instructions)
• Documentation says the “Flash Direction” register
allows you to choose whether the pin works as an
“in” pin or works as an “out” pin (common practice)
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CHANGE INTERFACING FROM ASM TO CPP CODE
InitFlashPortCPP( )
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InitFlashPortCPP( )
• Get the Port to work correctly as
output for pins PB5  PB0, leaving
other pins unchanged.
(Set as “Output” to control the lights)
Used during Write and Read operations
WARNING
STARTS
AT 0
BOTH BIT
AND LED
NAMES
Name of “OUR”
part
LED 5 Leftmost
on Blackfin panel
LED 4
LED 3
Write 1 to a bit -- turn on
Write 0 to a bit -- turn off
LED 2
LED1
LED0 Rightmost
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• Set direction to 1 (output) on lower 6 pins
leaving other direction values unchanged
• NEED TO REVIEW ENCM369 – OR assembly code instruction
needed – 8 bit values (byte) – READ, USE OR, WRITE
– Read EBIU “direction” register into processor core data
register (makes a copy) (HOW?)
– Set another processor data register to 0x3F (0011 1111).
• Need to know basic binary and hexadecimal patterns for common
numbers – decimal confusing when used to show “on” and “off”
values – no calculators allowed in exams and quizzes
– OR the two data registers (HOW?)
– Write “modified copy” back into “direction register”
(HOW?)
• PROBLEM to overcome – how do we do “byte”
read and writes to Blackfin memory using “C++”?
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CHANGE INTERFACING FROM ASM TO CPP CODE
Key issues -- InitFlashPortCPP()
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• Write ‘1’ (on) or ‘0’ (off) to the Port to
activate LEDs connected to pins PB5
 PB0, leaving other pins on that
port unchanged in value. (common practice)
LED 5 Leftmost
LED 4
LED 3
LED 2
LED1
CHANGE INTERFACING FROM ASM TO CPP CODE
WriteFlashLEDCPP( )
LED0
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• Write ‘1’ (on) or ‘0’ (off) to the Port to activate
LEDs connected to pins PB5  PB0, leaving
other pins unchanged.
HOW TO DO THIS OPERATION
1. Read 8-bit BYTE “LED data register” into 32-bit
processor data register (makes a copy in R1)
2. Keep “top” 2 bits (AND operation) of copied
value (8 bit) in 32-bit register
3. Keep “bottom” 6 bits of “in-par” 32-bit in_value
(R0) that is passed into the subroutine
4. OR the two processor data registers (R0, R1)
5. Write “modified 32-bit copy” back into “LED data
register” – 8-bit byte operation needed
EXAMPLE NOT YET BEING DONE IN HIGH LEVEL C++
Key issues WriteFlashLEDASM( input_value)
PROBLEM: “byte (8)” operations using word (32) sized registers
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Things we STILL need to learn
• How do we put a 32-bit value (long int) into
a register (data Rn or pointer Pn)?
• How do we put an 8 or 32-bit value into
memory?
• How do we handle byte operations (8-bit)?
• How do we do AND and OR operations on
Blackfin? – Do in ASM and CPP?
• How similar is Blackfin to MIPS when
handling these issues (ENCM369)?
Meaning can we use ENCM369 ideas with
the Blackfin?
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Agenda tackled
• Processors need to send out control
signals
– General purpose input / output GPIO on
processor
• Not enough GPIO lines
– FLASH memory chip has additional I/O ports
connected to Ez-Lite KIT LED’s
• What do we need to have happen to make
the FLASH memory work as we want?
• What new Blackfin assembly language
instructions do we need to learn?
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