nand2/06_IO_Devices/06_LCD

06 LCD

The special function register LCD memory mapped to addresses 4104 and 4105 enables HACK to write bytes to the LCD controller chip ILI9341V situated on MOD-LCD2.8RTP. The communication protocol is SPI with one additional wire DCX. The protocol defines transmission of 8 bit commands with DCX = 0 followed data with DCX=1. Data packets can have any length depending on the launched command.

Chip specification

IN/OUT	wire	function
IN	in[7:0]	byte to be sent.
IN	in[8]	=0 send byte and set CSX low
IN	in[8]	=1 pull CSX high without sending byte
IN	in[9]	value of DCX when transmitting a byte.
IN	load	initiates the transmission of a byte, when in[8]=0
IN	load16	initiates the transmission of 16 bit in[15:0]
OUT	out[15]	=0 chip is busy, =0 ready
OUT	DCX	=0 command, =1 data
OUT	SDO	serial data out
OUT	SCK	serial clock
OUT	CSX	chip select not

The special function register LCD communicates with ILI9341V LCD controller over 4 wire SPI.

When load=1 and in[8]=0 transmission of byte in[7:0] is initiated. CSX is goes low (and stays low even when transmission is completed). DCX is set to in[9]. The byte in[7:0] is send to SDO bitwise together with 8 clock signals on SCK. During transmission out[15] is 1. After 16 clock cycles transmission is completed and out[15] is set to 0.

When load=1 and in[8]=1 CSX goes high and DCX=in[9] without transmission of any bit.

When load16=1 transmission of word in[15:0] is initiated. CSX is goes low (and stays low even when transmission is completed). DCX is set to 1 (data). After 32 clock cycles transmission is completed and out[15] is set to 0.

Proposed Implementation

Use a Bit to store the state (0 = ready, 1 = busy) which is output to out[15]. Another two Bit store the state of DCX and CSX. Use a counter PC to count from 0 to 15 or 31 according to load/load16. Finally we need two connected BitShift8L. They will be loaded with the byte in[7:0] or the word in[15:0] to be send. After 8/16 bits are transmitted the module cleares out[15].

Memory map

The special function register LCD is mapped to memory map of HACK according to:

address	I/O device	R/W	function
4104	LCD	W	start transmittion of byte in[7:0]
4105	LCD	W	start transmittion of word in[15:0]
4104/4105	LCD	R	out[15]=1 busy, out[15]=0 idle

LCD in real hardware

The board MO-LCD2.8RTP comes with a 2.8 inch LCD screen controlled by a controller chip ILI8341V. MOD-LCD2.8RTP must be connected to iCE40HX1K-EVB with 6 jumper wire cables: +3.3V, GND plus 4 data wires according to iCE40HX1K-EVB.pcf (Compare with schematic iCE40HX1K_EVB and MOD-LCD2.8RTP_RevB.pdf.

set_io LCD_DCX 1        # PIO3_1A connected to pin 5 of GPIO1
set_io LCD_SDO 2        # PIO3_1B connected to pin 7 of GPIO1
set_io LCD_SCK 3        # PIO3_2A connected to pin 9 of GPIO1
set_io LCD_CSX 4        # PIO3_2B connected to pin 11 of GPIO1

wire	iCE40HX1K-EVB (GPIO1)	MOD-LCD2.8RTP (UEXT)
+3.3V	3	1 +3.3V
GND	4	2 GND
LCD_DCX	5	7 D/C
LCD_SDO	7	8 MOSI
LCD_SCK	9	9 SCK
LCD_CSX	11	11 CS

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Project

• Implement LCD.v and test with testbench:

  $ cd 06_LCD
  $ apio clean
  $ apio sim
  

• Compare output OUT of special chipLCD with CMP.

  

• Add special function registerLCD to HACK at memory addresses 4104/4105 and upload to iCE40HX1K-EVB with the bootloader boot.asm preloaded into ROM

  $ cd ../05_GO
  $ make
  $ cd ../00_HACK
  $ apio clean
  $ apio upload
  

• Proceed to 07_Operating_System and implement the driver class Screen.jack that sends command over LCD the controller chip ILI9341V on MOD-LCD2.8RTP