Lab 4 -- Introduction to SPI interfacingpeople.ucalgary.ca/.../16_Nov/16-10-14T_Lab4A.pdfLab 4 --...

Lab 4 -- Introduction to SPI interfacing

The problem The HD44780 device has an 11 bit

control register

R/W* -- Active low read / write*

RS* -- Active low – device accepts B7 – B0 lines as instructions

RS – Active high – device B7 – B0 lines as data

E E* -- Device operates on active low edge AND ignores levels

11/13/2016 SPI and LCD , Copyright M. Smith, ECE, University of Calgary, Canada

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The problem – Controlling 1 HD44780Parallel to Serial signal conversion

HD44780 has 11 control lines which MUST operate in PARALLEL

Too simple a device to use up 11 GPIO Lines

SOLUTION – Blackfin MASTER sends a 16-bit SERIAL signal to the HD44780 SLAVE over the SPI MOSI line

MOSI -- Master Out – Slave In

Also need GROUND wire to allow return of electrical signal


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The problem – Controlling 2 HD44780 HD44780 has 11 control lines which MUST operate in

PARALLEL

Blackfin MASTER sends a 16-bit SERIAL signal to the HD44780 SLAVE over the SPI MOSI line -- Master Out –Slave In

SOLUTION – Blackfin MASTER sends out a Chip Select (CS*) line to each ‘780. CS* means active

NEED AND QUERY – Blackfin must generate the signals automatically on PF5 and PF6 – Does this mean changes to My_Activate Switches( ) Lab 1?


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The problem – Controlling 2 HD44780 HD44780 has 11 control lines operate in PARALLEL

Blackfin MASTER sends a 16-bit SERIAL signal to the HD44780 SLAVE over the SPI MOSI line

Blackfin MASTER uses 2 CS* to control 2 ‘780 (ONLY 1 IN LAB 4).

PROBLEM – ‘780 ONLY accepts commands when E E*

PROBLEM – Blackfin is 50,000 times faster than ‘780

PROBLEM -- Command signals must be stable before we issue the accept commands

PROBLEM -- We want 5 different tasks to send messages to LCD screen with out being mixed up

PROBLEM -- We need to display temperature from Lab 3 (which now does not exist)

PROBLEM – How do we make SPI and ‘780 work?


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Demonstration

Initialize LCD – send series of “bit patterns” to be interpreted as INSTRUCTIONS – done once – uTTCOSg thread “Init_LCD( )”

Send message – send series of “bit patterns” to be interpreted as DATA – done many times uTTCOSg threads “MSG1()”, “MSG2( )”


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Lab 4 A is to demo these two steps manually (shows LCD hardware works)

Sec 01 / 03 – Friday 2 PM – 3 PM -- A301, A305 (1 – 8)

Sec 02 / 04 – Monday 8 AM – 9 AM – A301, A305 (1 – 8)OR Friday 2 PM – 3 PM -- A305 (9 - 16)


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uTTCOSg thread “Init_LCD( )”must perform the follow

These MUST be sent as INSTRUCTIONS (COMMAND RS = LOW) when data is stable (Fast Blackfin) and on signal edge E E*


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uTTCOSg thread “Mesg_511( )”must perform the follow

These MUST be sent as DATA (COMMAND RS = HIGH) when data is stable (Fast Blackfin) and on signal edge E E*


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Demonstration

Get out Lab 1 instructions with 2 steps

Initialize LCD – send series of “bit patterns” to be interpreted as INSTRUCTIONS – done once – uTTCOSg thread “Init_LCD( )”

Send message – send series of “bit patterns” to be interpreted as DATA – done many times uTTCOSg threads “MSG1()”, “MSG2( )”


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Lab 4 A – Shows LCD works

Lab 4 B – Get uTTCOS threads demonstrated

Lab 4 C – Show basic SPI operations work

Lab 4 D – Get 4B and 4C to work together and display messages on LCD screen (without destroying each other)


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Lab 4 – Top Down Development -- Profound Procrastinated Programming

Init_uTTCOs( ); Init_LED( ); Init_SWs( );

AddThread(FlashLED6, NO_DELAY, EVERY_SECOND);

AddThread(MOCK_SPI_controller, NO_DELAY, EVERY 1 / 20 S) // Make Faster Later

AddThread(Init_SPI, 1s_DELAY, RUN_ONCE) AddThread(MSG0, 3s_DELAY + 0/2 s, EVERY_2_SECS); AddThread(MSG1, 3s_DELAY + 1/2 s, EVERY_2_SECS);

AddThread(MSG2, 3s_DELAY + 2/2s , EVERY_2_SECS);

AddThread(DisplayLAB3Temperature, 2s_DELAY + 3/2s , EVERY_15_SECS);

Start_uTTCOS( ); while(1) { Sleep( ); Dispatch_Tasks( );11/13/2016 SPI and LCD ,

Copyright M. Smith, ECE, University of Calgary, Canada12 / 30

Step 1 – Check that threads work correctly – Do Code review


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// This is basically a variation of Lab 1

void SPI_controller(void) { FlashLED5( ); },

void Init_SPI(void) { TurnOn LED1( ); } // Show done

void MSG0(void) { FlashLED2( ); }void MSG1(void) { FlashLED3( ); }void MSG2(void) { /* STUB */ ;}

void DisplayLAB3Temp (void) { FlashLED4( ); }}

Step 2 – Set up threads work correctly – Do Code review


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void SPI_controller(void) { FlashLED5( ); }, void Init_SPI(void) {TurnOn LED1( ); } // Show donevoid MSG0(void) {FlashLED2( ); }void MSG1(void) {FlashLED3( ); }void MSG2(void) { /* STUB */ ;}

static float ChinookTemp[10] = { 24.0, 26.0, 28.0, 29.0, 33.0, -35.0, -34.0, -20.0};

float currentTemp = 0;float GetTemperature_TMP03(void) {

static int mockTempIndex = -1; mockTempIndex++;if (mockTempIndex >= 10) mockTempIndex = 0;return ChinookTemp[mockTempIndex];

}void LAB3_temp(void) {

static int mockTempIndex = 0;currentTemp = ChinookTemp[mockTempIndex ++];if (mockTempIndex >= 10) mockTempIndex = 0;

Step 2A Set up message threads

extern bool commandStringBeingSent;

extern bool commandStringToSend;

extern bool commandStringIsInstruction;

extern char SPI_MessageBuffer[256];

void MSGX(void) {

Flash_LEDX();if (commandStringBeingSent = true) return;

if (commandStringToSend == true) return;

commandStringToSend = 1; // uTTCOSg guarentees NO DATA RACE

commandStringIsInstruction = false;

strcpy(SPI_MessageBuffer, “This is Message X”);

}11/13/2016 SPI and LCD ,

Copyright M. Smith, ECE, University of Calgary, Canada15 / 30

Step 2B Set up temp thread

extern bool commandStringBeingSent; extern bool commandStringToSend;

extern bool commandStringIsInstruction; extern char SPI_MessageBuffer[256];

void LAB3_temp {void)

Flash_LEDX();if (commandStringBeingSent = true) return;

if (commandStringToSend == true) return;

commandStringToSend = 1; // uTTCOSg guarentees NO DATA RACE

commandStringIsInstruction = false;

float currentTemp = GetTemperature_TMP03( );

sprintfSPI_MessageBuffer,“Current temperature is %5.2f”, currentTemp);

}


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Step 2B -- Set up temp thread

static float ChinookTemp[10] = { 24.0, 26.0, 28.0, 29.0, 33.0, -35.0, -34.0, -20.0};

float currentTemp_Lab3 = 0;

#define LAB3_MOCKED 1

float GetTemperature_TMP03(void) {#if LAB3_MOCKED

static int mockTempIndex = -1;

mockTempIndex++;if (mockTempIndex >= 10) mockTempIndex = 0;currentTemp_lab3 = ChinookTemp[mockTempIndex];

#endif

return currentTemp_Lab3}


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Step 2 C Simple Mock of SPI controller


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bool commandStringBeingSent = false; bool commandStringToSend = false;bool commandStringIsInstruction = false; char SPI_MessageBuffer[256];unsigned char commandsToSend = 0; unsigned char commandsSent = 0;extern unsigned char id_SendSPICommandString;#define SPI_MOCK_LEVEL 1void SPI_controller(void) {

FlashLED5( ); if (commandStringToSend == false) return; // No messageif (commandStringBeingSent == true) return;commandStringBeingSent = true;commandsToSend = strlen(SPI_MessageBuffer[);commandsSent = 0;id_SendSPICommandString =

AddThread(SendSPICommandString, NO_DELAY, 1 / 20 s);}

Step 2C – Simple Mock of SPI controller

extern bool commandStringBeingSent; extern bool commandStringToSend;

extern bool commandStringIsInstruction; extern char SPI_MessageBuffer[256];

extern unsigned char commandsToSend; extern unsigned char commandsSent;unsigned char id_SendSPICommandString = 0

#define MOCK_LEVEL 1void SendSPICommandString(void) {

#if (MOCK_LEVEL == 1)

if (commandStringIsInstruction)

printf(“INSTR: %s\n”, SPI_MessageBuffer);else printf(“DATA: %s\n”, SPI_MessageBuffer);

commandStringBeingSent = false;

commandStringToSend = false;

commandsToSend = 0;

DeleteThread(id_SendSPICommandString );

#endif

} 11/13/2016 SPI and LCD , Copyright M. Smith, ECE, University of Calgary, Canada

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Step 3A – Mock of SPI controller not always ready

void SendSPICommandString(void) {

#if (MOCK_LEVEL == 2)

if (commandsToSend == 0) return;

if (MOCK_IS_SPI_Ready( ) == false) return;

MOCK_SPI_Send(commandStringIsInstruction, (unsigned int) SPI_MessageBuffer[commandsSent++]);

commandsToSend--;

if (commandsToSend == 0) {

MOCK_SPI_Send(commandStringIsInstruction, (unsigned int) ‘\n’);

commandsSent = 0; SPI_MessageBuffer[commandsSent++]);

commandStringBeingSent = false;

commandStringToSend = false;

DeleteThread(id_SendSPICommandString );}

#endif

}


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Step 3B – Mock of SPI controller not always ready

bool MOCK_IS_SPI_Ready(void) { // Ready 1 time in 5int value = rand( ) % 5; if (value == 1) return true; else return false;

}

bool newMessage = true;void MOCK_SPI_Send(bool commandStringIsInstruction,

unsigned int commandToSend) {if (newMessage) { newMessage = false;

if (commandStringIsInstruction) printf(“INSTR: ”); // NO \n, else printf(“DATA: ”);

}

printf(“%c”, (char) commandToSend);

if (commandToSend == (unsigned int) ‘\n’)newMessage = true;

}


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Step 4A – Any easy SPI stuff we can understand all ready?

Any write to 16 bit SPI Transmit Data Buffer Register (SPI_TDBR) causes something to occur.

NOTE SPI_TDBR is hardware double buffered in a special way


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Step 4B – Any easy SPI stuff we can understand all readySPI is a serial line – needs to transmit 16 things one after another – NOT in parallel

NOTE SPI_F is a R O bit


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Things still unknown

How to hook 11 bit LCD screen to 1 bit SPI line which has 16 bits in a stream

How to do SPI_Hardware_Init( )

How to do SPI_Hardware_Start( )

How to understand SPI Architecture


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Lab. 4


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Blackfin processorRunning tasks using TTCOS operating system with SPI message sender(Small SPI-OS)

SPI-interface4 wires + 2

chip select lines

SPI-bus

SPI-interface

External parallel I/O(Blackfin Extender)

4 wires

4 wires + 2 chip select lines(serial communication)

12 wires(Parallel

Communication)

OPTIONALcar control

(if want all 4 labs runningOPTIONAL

Assignment 2 SPI LCD GUI 4 wires

(ParallelCommunication)

4 wires + 1 chip select line(serial communication)

SPI Hardware


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SPI Timing


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SPI Control Register


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You have already met


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SPI Speed control register


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SPI – Flag Register


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Lab 4 -- Introduction to SPI interfacingpeople.ucalgary.ca/.../16_Nov/16-10-14T_Lab4A.pdfLab 4 --...

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