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Getting the O in I/O to work on a typical microcontroller

Getting the O in I/O to work on a typical microcontroller. Activating a FLASH memory “output line” Part 1 Main part of Laboratory 1 Also needed for “voice activated car control project”. Agenda. Processors need to send out control signals (high / low 1 / 0 true / false)

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Getting the O in I/O to work on a typical microcontroller

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  1. Getting the O in I/O to workon a typical microcontroller Activating a FLASH memory “output line”Part 1 Main part of Laboratory 1Also needed for “voice activated car control project”

  2. Agenda • Processors need to send out control signals (high / low 1 / 0 true / false) • General purpose input / output lines (GPIO lines) on processor 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? Blackfin BF533 I/O

  3. Programmable Flags • Most micro-controllers have general purpose input or output lines capable of generating “true” or “false” values • Blackfin 533 has 16 GPIO lines Blackfin BF533 I/O

  4. Where are the GPIO pins found? Blackfin BF533 I/O

  5. 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 • Audio Control • Input -- Buttons – GPIO PF8, 9, 10, 11 • Output – GPIO PF0, 1, 6, 7 • SPI interface control -- PF5 • Pins are functionally multiplexed – meaning pins can perform different functions at different times . Blackfin BF533 I/O

  6. Additional I/O pins available Blackfin BF533 I/O

  7. Need to control LED on board • Controlled using special “additional” parallel port interface attached to “flash” memory chip PROJECT USE LEDs used to indicatedirection radio-controlledcar will move LEFTRIGHTFORWARDBACK CONTROL ON Blackfin BF533 I/O

  8. FLASH MEMORY UNIT • Major task -- Contains the code need to “boot” (start) the processor 2 PSD4256G6V From STMicroElectronics The FLASH part we need during Lab. 1 Additional I/O pins Blackfin BF533 I/O

  9. LEDs connected to FLASH port BACKFORWARDRIGHTLEFT??? CONTROL ON These pins are connected to other things on the board DON’T CHANGEBEHAVIOUR Blackfin BF533 I/O

  10. Steps to activating LEDs • Get the FLASH memory to work correctly • Write the code for InitFlashASM( ) • Get the Port to work correctly as output for pins PB5  PB0, leaving other pins unchanged • Write the code for InitFlashPortASM( ) • Write the value we want to LEDs • WriteFlashLEDASM( int value) • Read back the value the LEDs show • int ReadFlashLEDASM( ) Blackfin BF533 I/O

  11. FLASH MEMORY UNIT • Controlled through “EBIU”External Bus Interface UnitEBIU are common on most processors (although often by different name) FLASH SDRAMCONTROLLER Blackfin BF533 I/O

  12. 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 is to go to FLASH or SDRAM units????? Blackfin BF533 I/O

  13. 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, control car later. Blackfin BF533 I/O

  14. What we know • When the processor powers up – it must read its “boot” program from the FLASH • 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. (common practice) • The first part of the program the processor reads in (boot code) can change the processor to read FLASH more efficiently (faster) Blackfin BF533 I/O

  15. Controlling FLASH operation What we need to worry about It is common for most microcontroller peripherals to have a “GLOBAL” control register and one or more “specific” control registers Blackfin BF533 I/O

  16. InitFlashASM( ) • 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 InitFlashASM( ) may have already been called by another thread before you use it • InitFlashASM( ) { /* Concept only */ If FLASH memory already configured – return without changing the initialization Else { configure Memory Bank control register THEN configure Global control (turns on the FLASH) } } Blackfin BF533 I/O

  17. Set the Bank control register • Reset value will probably work “as is” but not efficient – “slow reads” by default (common practice for hardware) Default Slow (15 cycle) read and write operations Blackfin BF533 I/O

  18. Settings control access speed DEFAULT Processor sends out address and waits 15 cycles before “do a read operation” to memory. The processor waits another 15 cycles before the actual read occurs. Blackfin BF533 I/O

  19. Set General Control Register • Reset value leaves “CLKOUT” disabled – is that important? What parts of the operation of this register must we “know” Unanswered at this time. We don’t know what needs to be known Blackfin BF533 I/O

  20. InitFlashPortASM( ) • Get the Port to work correctly as output for pins PB5  PB0, leaving other pin behaviour (6 and 7) unchanged. • 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) Blackfin BF533 I/O

  21. InitFlashPortASM( ) • 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 Leftmost LED 5 LED 4 LED 3 LED 2 LED1 LED0 Blackfin BF533 I/O

  22. Key issues -- InitFlashPortASM() • 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 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++”? Blackfin BF533 I/O

  23. WriteFlashLEDASM( ) • 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) Leftmost LED 5 LED 4 LED 3 LED 2 LED1 LED0 Blackfin BF533 I/O

  24. Key issues WriteFlashLEDASM( in_value) • Write ‘1’ (on) or ‘0’ (off) to the Port to activate LEDs connected to pins PB5  PB0, leaving other pins unchanged. • Read “LED data register” into processor data register (makes a copy in R0) – 8-bit byte • Keep “top” 2 bits (AND operation) of copy (8 bit) • Keep “bottom” 6 bits of “in-par” 32-bit in_value that is passed into the subroutine • OR the two processor data registers (32 and 8) • Write “modified copy” back into “LED data register” – 8-bit byte • PROBLEM mixed “byte (8)” and “long word (32)” operations Blackfin BF533 I/O

  25. Things we 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? • How similar is Blackfin to MIPS when handling these issues (ENCM369)? Blackfin BF533 I/O

  26. 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? Blackfin BF533 I/O

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