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

2. 6/3/2015 SPI and LCD, Copyright M. Smith, ECE, University of Calgary, Canada 2 / 30 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?

3. 6/3/2015 SPI and LCD, Copyright M. Smith, ECE, University of Calgary, Canada 3 / 30 LCD Connection information 13 key connections

4. 6/3/2015 SPI and LCD, Copyright M. Smith, ECE, University of Calgary, Canada 4 / 30 Data Bus Connections for LCD screen From CJ7 connector on Blackfin interface BQ0 BQ1 BQ2 BQ3 BQ4 BQ5 BQ6 BQ7

5. 6/3/2015 SPI and LCD, Copyright M. Smith, ECE, University of Calgary, Canada 5 / 30 Power Connections for LCD screen From LOGIC LAB POWER GROUND +5V

6. 6/3/2015 SPI and LCD, Copyright M. Smith, ECE, University of Calgary, Canada 6 / 30 LCD operations require certain values on RS, R/W* and DBx lines LCD COMMANDS RSR/W*DATA DB7 to DB0 ClearScreen( )000x01 CursorIncrease( )000x05 CursorMove( )000x10 DisplayOn( )000x0B WriteLetter(value)10value WriteLetter(‘a’)100x61 (ascii ‘a’) WriteLetter(‘A’)100x41 (ascii ‘A’)

7. 6/3/2015 SPI and LCD, Copyright M. Smith, ECE, University of Calgary, Canada 7 / 30 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)

8. 6/3/2015 SPI and LCD, Copyright M. Smith, ECE, University of Calgary, Canada 8 / 30 The “idea” of how to cause the LCD to -- Clear the screen LCD COMMANDS RSR/W*DATA DB7 to DB0 ClearScreen( )000x01 That means we must send the following “voltage” signals to the LCD pins RS R/W E DB7 DB6 DB5 DB4 DB3 DB2 DB1 DB0 0 0 1 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 1 // EnableStrobe 0 0 1 0 0 0 0 0 0 0 1 And we must wait after sending each “signal” for sufficient time for the LCD to work. The LCD probably works 100000 times slower than Blackfin.

9. 6/3/2015 SPI and LCD, Copyright M. Smith, ECE, University of Calgary, Canada 9 / 30 To cause the “slow” LCD to Clear the screen LCD COMMANDS RSR/W*DATA DB7 to DB0 ClearScreen( )000x01 That means we must send the following “voltage” signals to the LCD pins RS R/W E DB7 DB6 DB5 DB4 DB3 DB2 DB1 DB0 0 0 1 0 0 0 0 0 0 0 1 Wait( ) 0 0 0 0 0 0 0 0 0 0 1 // EnableStobe Wait( ) 0 0 1 0 0 0 0 0 0 0 1 Wait( )

10. 6/3/2015 SPI and LCD, Copyright M. Smith, ECE, University of Calgary, Canada 10 / 30 LCD Command Instruction set

11. 6/3/2015 SPI and LCD, Copyright M. Smith, ECE, University of Calgary, Canada 11 / 30 Details of what is needed

12. 6/3/2015 SPI and LCD, Copyright M. Smith, ECE, University of Calgary, Canada 12 / 30 LCD Command Instruction set For some commands the LCD is very slow 1.640 ms For other commands the LCD is faster 0.040 ms = 40 us Remember the Blackfin instruction is around 0.000002 ms = 2 ns

13. 6/3/2015 SPI and LCD, Copyright M. Smith, ECE, University of Calgary, Canada 13 / 30 To cause the LCD to Clear the screen LCD COMMANDS RSR/WDATA DB7 to DB0 ClearScreen( )000x01 That means we must send the following “voltage” signals to the LCD pins RS R/W E DB7 DB6 DB5 DB4 DB3 DB2 DB1 DB0 0 0 1 0 0 0 0 0 0 0 1 Wait(1.64 ms ) -- Only one of these is really needed this long – Refactor later 0 0 0 0 0 0 0 0 0 0 1 // EnableStobe Wait( 1.64 ms ) -- Only one of these is really needed this long – Refactor later 0 0 1 0 0 0 0 0 0 0 1 Wait( 1.64 ms) -- Only one of these is really needed this long – Refactor later Remember – when shorten down – still must worry about Speed

14. 6/3/2015 SPI and LCD, Copyright M. Smith, ECE, University of Calgary, Canada 14 / 30 To cause the LCD to write the letter ‘A’ on its screen LCD COMMANDS RSR/WDATA DB7 to DB0 WriteLetter(value)10value WriteLetter(‘a’)100x61 That means we must send the following “voltage” signals to the LCD pins RS R/W E DB7 DB6 DB5 DB4 DB3 DB2 DB1 DB0 1 0 1 0 1 1 0 0 0 0 1 Wait( 40 us) 1 0 0 0 1 1 0 0 0 0 1 // EnableStobe Wait( 40 us) 1 0 1 0 1 1 0 0 0 0 1 Wait( 40 us)

15. 6/3/2015 SPI and LCD, Copyright M. Smith, ECE, University of Calgary, Canada 15 / 30 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 01000001 = 0x41 sent to LCD data pins WriteSPI(‘A’); Also send the necessary LCD control signals (EN / RS)

16. 6/3/2015 SPI and LCD, Copyright M. Smith, ECE, University of Calgary, Canada 16 / 30 Alpha-numeric ascii code ‘A’ to ‘Z’, ‘a’ to ‘z’

17. 6/3/2015 SPI and LCD, Copyright M. Smith, ECE, University of Calgary, Canada 17 / 30 Alpha-numeric ascii code 0 through 9, ( ) etc

18. 6/3/2015 SPI and LCD, Copyright M. Smith, ECE, University of Calgary, Canada 18 / 30 Problem – we need 22 lines (in / out) to control LCD – and we don’t have them on the Blackfin

19. 6/3/2015 SPI and LCD, Copyright M. Smith, ECE, University of Calgary, Canada 19 / 30 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

20. 6/3/2015 SPI and LCD, Copyright M. Smith, ECE, University of Calgary, Canada 20 / 30 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”

21. 6/3/2015 SPI and LCD, Copyright M. Smith, ECE, University of Calgary, Canada 21 / 30 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

22. 6/3/2015 SPI and LCD, Copyright M. Smith, ECE, University of Calgary, Canada 22 / 30 Known facts -- MOSI data is transmitted from Blackfin the moment that data is written to Blackfin SPI_TDBR register SPI_TDBR Blackfin Processor SPI_RXBR LCD SCREEN CJ7 / CJ8 SWITCHES (LOGIC LAB) SLAVE INPUT INTERFACE SLAVE OUTPUT INTERFACE MOSIMISO SLAVE SELECT PF5 used (PF1 to PF7) DATA CONTROL SPI CLOCK LOAD Slave to LCD

23. 6/3/2015 SPI and LCD, Copyright M. Smith, ECE, University of Calgary, Canada 23 / 30 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 ignore the command unless the slave select line is held low 

24. 6/3/2015 SPI and LCD, Copyright M. Smith, ECE, University of Calgary, Canada 24 / 30 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 LCD SCREEN CJ7 / CJ8 SWITCHES (LOGIC LAB) SLAVE INPUT INTERFACE SLAVE OUTPUT INTERFACE MOSIMISO SLAVE SELECT PF5 used (PF1 to PF7) DATA CONTROL SPI CLOCK LOAD Slave to LCD

25. 6/3/2015 SPI and LCD, Copyright M. Smith, ECE, University of Calgary, Canada 25 / 30 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 ACCEPTS 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 or  ????

26. 6/3/2015 SPI and LCD, Copyright M. Smith, ECE, University of Calgary, Canada 26 / 30 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 LCD SCREEN CJ7 / CJ8 SWITCHES (LOGIC LAB) SLAVE INPUT INTERFACE SLAVE OUTPUT INTERFACE MOSIMISO SLAVE SELECT PF5 used (PF1 to PF7) DATA CONTROL SPI CLOCK LOAD Slave to LCD

27. 6/3/2015 SPI and LCD, Copyright M. Smith, ECE, University of Calgary, Canada 27 / 30 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!

28. 6/3/2015 SPI and LCD, Copyright M. Smith, ECE, University of Calgary, Canada 28 / 30 Blackfin transmits 16 bits with THIS format over the MOSI line DB7, DB6, ………DB1, DB0 RS 1 – LCD data 0 – LCD instruction R/W 1 – Read from LCD 0 – Write to LCD 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 )

29. 6/3/2015 SPI and LCD, Copyright M. Smith, ECE, University of Calgary, Canada 29 / 30 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 DB0 1 0 1 0 1 1 0 0 0 0 1 1 0 0 0 1 1 0 0 0 0 1 // EnableStobe 1 0 1 0 1 1 0 0 0 0 1 ClearScreen ‘4’ ‘1’ ‘5’

30. 6/3/2015 SPI and LCD, Copyright M. Smith, ECE, University of Calgary, Canada 30 / 30 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?