1. HD44780 LCD programming From the Hardware Side
Design and implementation details on the way to a valid SPI-LCD interface driver

2. SPI and LCD , Copyright M. Smith, ECE, University of Calgary, Canada
To be tackled today
What commands are necessary to control the LCD device -- HD44780?
How do you send commands from the Blackfin to a LCD device?
How do we get the timing correct?
2/16/2019
SPI and LCD , Copyright M. Smith, ECE, University of Calgary, Canada

3. LCD Connection information
13 key connections
2/16/2019
SPI and LCD , Copyright M. Smith, ECE, University of Calgary, Canada

4. Data Bus Connections for LCD screen
From CJ7 connector on Blackfin interface BQ0 BQ1 BQ2 BQ3 BQ4 BQ5 BQ6 BQ7
2/16/2019
SPI and LCD , Copyright M. Smith, ECE, University of Calgary, Canada

5. Power Connections for LCD screen
From LOGIC LAB POWER
GROUND
+5V
2/16/2019
SPI and LCD , Copyright M. Smith, ECE, University of Calgary, Canada

6. LCD operations require certain values on RS, R/W* and DBx lines
LCD COMMANDS RS
R/W*
DATA DB7 to DB0
ClearScreen( )
0x01
CursorIncrease( )
0x05
CursorMove( )
0x10
DisplayOn( )
0x0B
WriteLetter(value) 1
value
WriteLetter(‘a’)
0x61 (ascii ‘a’)
WriteLetter(‘A’)
0x41 (ascii ‘A’)
2/16/2019
SPI and LCD , Copyright M. Smith, ECE, University of Calgary, Canada

7. Control Line Connections for LCD screen
From CJ8 connector on Blackfin interface BQ8 RS command (0) or data (1) control BQ9 R/W* Read (1) from LCD Write (0) to LCD
BQ10 E Enable Normally 1
Transition 1  0 makes the LCD work (accept the command or data information)
2/16/2019
SPI and LCD , Copyright M. Smith, ECE, University of Calgary, Canada

8. The “idea” of how to cause the LCD to -- Clear the screen
LCD COMMANDS RS
R/W*
DATA DB7 to DB0
ClearScreen( )
0x01
That means we must send the following “voltage” signals to the LCD pins
RS R/W E DB7 DB6 DB5 DB4 DB3 DB2 DB1 DB
// EnableStrobe
// LCD reads on high to low
And we must wait after sending each “signal” for sufficient time for the LCD to work. The LCD probably works times slower than Blackfin.
2/16/2019
SPI and LCD , Copyright M. Smith, ECE, University of Calgary, Canada

9. To cause the “slow” LCD to Clear the screen
LCD COMMANDS RS
R/W*
DATA DB7 to DB0
ClearScreen( )
0x01
That means we must send the following “voltage” signals to the LCD pins
RS R/W E DB7 DB6 DB5 DB4 DB3 DB2 DB1 DB WasteSomeTimeCPP( )
// EnableStobe
WasteSomeTimeCPP( )
2/16/2019
SPI and LCD , Copyright M. Smith, ECE, University of Calgary, Canada

10. LCD Command Instruction set
2/16/2019
SPI and LCD , Copyright M. Smith, ECE, University of Calgary, Canada

11. Details of what is needed
2/16/2019
SPI and LCD , Copyright M. Smith, ECE, University of Calgary, Canada

12. LCD Command Instruction set
For some commands the LCD is very slow ms
For other commands the LCD is faster ms = 40 us
Remember the Blackfin instruction is around ms = 2 ns
2/16/2019
SPI and LCD , Copyright M. Smith, ECE, University of Calgary, Canada

13. To cause the LCD to Clear the screen
LCD COMMANDS RS
R/W
DATA DB7 to DB0
ClearScreen( )
0x01
That means we must send the following “voltage” signals to the LCD pins
RS R/W E DB7 DB6 DB5 DB4 DB3 DB2 DB1 DB Wait(1.64 ms ) Only one of these is really needed this long – Refactor later
// EnableStobe
Wait( 1.64 ms ) -- Only one of these is really needed this long – Refactor later
Wait( 1.64 ms) -- Only one of these is really needed this long – Refactor later Remember – when shorten down – still must worry about Speed
2/16/2019
SPI and LCD , Copyright M. Smith, ECE, University of Calgary, Canada

14. To cause the LCD to write the letter ‘A’ on its screen
LCD COMMANDS RS
R/W
DATA DB7 to DB0
WriteLetter(value) 1
value
WriteLetter(‘a’)
0x61
That means we must send the following “voltage” signals to the LCD pins
RS R/W E DB7 DB6 DB5 DB4 DB3 DB2 DB1 DB Wait( 40 us)
// EnableStobe
Wait( 40 us)
2/16/2019
SPI and LCD , Copyright M. Smith, ECE, University of Calgary, Canada

15. Bit patterns to send a character
Complicated or not?
How do the letter bit patterns for the LCD data patterns relate to ASCII bit patterns?
standard format used to store characters in a C++ character array?
Just copy from an array onto the LCD data pins
To cause “A” to appear on LCD screen need bit pattern = 0x41 sent to LCD data pins WriteSPI(‘A’);
Also send the necessary LCD control signals (EN / RS)
2/16/2019
SPI and LCD , Copyright M. Smith, ECE, University of Calgary, Canada

16. Alpha-numeric ascii code ‘A’ to ‘Z’, ‘a’ to ‘z’
2/16/2019
SPI and LCD , Copyright M. Smith, ECE, University of Calgary, Canada

17. Alpha-numeric ascii code 0 through 9, ( ) etc
2/16/2019
SPI and LCD , Copyright M. Smith, ECE, University of Calgary, Canada

18. SPI and LCD , Copyright M. Smith, ECE, University of Calgary, Canada
Problem – we need 22 lines (11 in / 11 out) to control LCD – and we don’t have them on the Blackfin
2/16/2019
SPI and LCD , Copyright M. Smith, ECE, University of Calgary, Canada

19. Solution – Setup LCD as SLAVE device Master (Blackfin) / Slave (LCD) concept
Will not work
LCD was set up as a PARALLEL DEVICE – many lines at one time
Not capable of MOSI control
MOSI --MASTER OUT – SLAVE IN
2/16/2019
SPI and LCD , Copyright M. Smith, ECE, University of Calgary, Canada

20. SPI and LCD , Copyright M. Smith, ECE, University of Calgary, Canada
Solution
There is a standard chip (Name ?????) that is capable of
Receiving (serial) signals from the Blackfin over the MOSI wire
Converting those serial signals (16 signals -- received one at a time) into a parallel signal (16 signals -- sent all at once)
Sending the PARALLEL voltage signals to the LCD
This chip has been designed into the Logic Station Blackfin interface (is not part of the Blackfin itself
All we need to do is attach 11 wires from the interface to the LED
Attach 4 wires from the interface to the Blackfin MOSI lines
Program the Blackfin SPI interface and “GO”
2/16/2019
SPI and LCD , Copyright M. Smith, ECE, University of Calgary, Canada

21. Lots of stuff has to happen in the correct order
Putting data into the Blackfin SPI_TDBR register causes the data to be transmitted over the MOSI line
SPI_TDBR means Serial Parallel Interface Transmit Data Buffer Register
2/16/2019
SPI and LCD , Copyright M. Smith, ECE, University of Calgary, Canada

22. Known facts -- MOSI data starts being transmitted from Blackfin THE MOMENT that ANY data is written to Blackfin SPI_TDBR register
SPI_TDBR Blackfin Processor SPI_RXBR
SLAVE SELECT PF5 used (PF1 to PF7)
SPI CLOCK
MOSI
MISO
SLAVE OUTPUT INTERFACE
SLAVE INPUT INTERFACE
LOAD Slave to LCD
DATA
SWITCHES (LOGIC LAB)
CONTROL
LCD SCREEN CJ7 / CJ8
2/16/2019
SPI and LCD , Copyright M. Smith, ECE, University of Calgary, Canada

23. Lots of stuff has to happen in the correct order
Putting (8-bit parallel) data into the Blackfin SPI_TDBR register causes the (1-bit serial) data to be transmitted over the MOSI line 
However the external device will ignore the command unless the slave select line is held low 
2/16/2019
SPI and LCD , Copyright M. Smith, ECE, University of Calgary, Canada

24. Known facts -- MOSI data is accepted by the SLAVE IF slave-select is active low – set PF5 to low – Master/Slave
SPI_TDBR Blackfin Processor SPI_RXBR
SLAVE SELECT PF5 used (PF1 to PF7)
SPI CLOCK
MOSI
MISO
SLAVE OUTPUT INTERFACE
SLAVE INPUT INTERFACE
LOAD Slave to LCD
DATA
SWITCHES (LOGIC LAB)
CONTROL
LCD SCREEN CJ7 / CJ8
2/16/2019
SPI and LCD , Copyright M. Smith, ECE, University of Calgary, Canada

25. Lots of stuff has to happen in the correct order
Putting data into the Blackfin SPI_TDBR register causes the data to be transmitted over the MOSI line 
However the external device will ACCEPT the command if the slave select line PF5 line is AUTOMATICALLY SET LOW by the Blackfin before the transmission is started. 
When transmission is ended (16-bits sent) then the slave select line PF5 line is AUTOMATICALLY SET HIGH by the Blackfin  or  ????
2/16/2019
SPI and LCD , Copyright M. Smith, ECE, University of Calgary, Canada

26. Known facts – The SLAVE only sends the data to the LCD when the PF5 line goes from low to high – interface design
SPI_TDBR Blackfin Processor SPI_RXBR
SLAVE SELECT PF5 used (PF1 to PF7)
SPI CLOCK
MOSI
MISO
SLAVE OUTPUT INTERFACE
SLAVE INPUT INTERFACE
LOAD Slave to LCD
DATA
SWITCHES (LOGIC LAB)
CONTROL
LCD SCREEN CJ7 / CJ8
2/16/2019
SPI and LCD , Copyright M. Smith, ECE, University of Calgary, Canada

27. Lots of stuff has to happen in the correct order
Putting data into the Blackfin SPI_TDBR register causes the data to be transmitted over the MOSI line 
However the external device will ACCEPT the command as the slave select line PF5 line is AUTOMATICALLY SET LOW by the Blackfin before the transmission is started. 
When transmission is ended (16-bits sent) then the slave select line PF5 line is AUTOMATICALLY SET HIGH by the Blackfin 
As PF5 line goes high the data sent by the Blackfin over the MOSI line to the special interface is transferred to the LCD 
Everything in the garden is wonderful!!!!!!!!!!!!!!
ALL? we have to do is make it happen! 
2/16/2019
SPI and LCD , Copyright M. Smith, ECE, University of Calgary, Canada

28. Blackfin transmits 16 bits with THIS format over the MOSI line
DB7, DB6, ………DB1, DB0
E – Enable / Strobe
1  0 – When this line goes from high to the low, then the command is send to (latched into) LCD
To make LCD respond to command 0x4F0 Then Blackfin must transmit 0x5F0 ( E High ) 0x4F0 ( E low ) 0x5F0 ( E high ) RS
1 – LCD data
0 – LCD instruction
R/W
1 – Read from LCD
0 – Write to LCD
2/16/2019
SPI and LCD , Copyright M. Smith, ECE, University of Calgary, Canada

29. SPI and LCD , Copyright M. Smith, ECE, University of Calgary, Canada
Design the controls signals and data signals to ‘Clear the screen’ and then send the char string “415” to LCD
Reminder – sequence to sent the letter ‘a” to the screen
RS R/W E DB7 DB6 DB5 DB4 DB3 DB2 DB1 DB // EnableStobe
ClearScreen
‘4’
‘1’
‘5’
2/16/2019
SPI and LCD , Copyright M. Smith, ECE, University of Calgary, Canada

30. SPI and LCD , Copyright M. Smith, ECE, University of Calgary, Canada
Tackled today
What commands are necessary to control the LCD device -- HD44780?
How do you send commands from the Blackfin to a LCD device?
How do we get the timing correct?
2/16/2019
SPI and LCD , Copyright M. Smith, ECE, University of Calgary, Canada