I have this code that needs modifying to be able to accept a keyboard input and then transmit to serial window UART #1, 2 or 3 by creating a loop that receives from UART 1 then Transmit to UART 1. I am a little perplexed on how to begin this code because I have only been dealing with loading string texts loaded in memory. Any assistance would be helpful.
; modified UART code for LPC2104 from Hohl and Hinds, Section 16.2.5 ; The modifications are to use push/pop instead of stmia/ldmdb area uartdemo, code, readonly pinsel0 equ 0xe002c000 ; controls function of pins u1start equ 0xe000c000 ; start of UART0 registers lcr0 equ 0xc ; line control register for UART0 lsr0 equ 0x14 ; line status register for UART0 ramstart equ 0x40000000 ; start of onboard RAM for 2104 stackstart equ 0x40000200 ; start of stack entry start ldr sp, = stackstart ; set up stack pointer bl UARTConfig ; initialize/configure UART0 ldr r1, = CharData ; starting address of characters ;input loop ldrb r0, [r1], #1 ; load character, increment address cmp r0, #0 ; null terminated? blne Transmit ; send character to UART bne loop ; continue if not a '0' done b done ; otherwise, we are done ; subroutine UARTConfig ; Configures the I/O pins first. ; Then sets up the UART control register. ; Parameters set to 8 bits, no parity, and 1 stop bit. ; Registers used: ; r5 - scratch register ; r6 - scratch register ; inputs: none ; outputs: none UARTConfig push {r5, r6, lr} ldr r5, = pinsel0 ; base address of register ldr r6, [r5] ; get contents bic r6, r6, #0xf ; clear out lower nibble orr r6, r6, #0x5 ; sets P0.0 to Tx0 and P0.1 to Rx0 str r6, [r5] ; r/modify/w back to register ldr r5, = u1start mov r6, #0x83 ; set 8 bits, no parity, 1 stop bit strb r6, [r5, #lcr0] ; write control byte to LCR mov r6, #0x61 ; 9600 baud @ 15MHz VPB clock strb r6, [r5] ; store control byte mov r6, #3 ; set DLAB = 0 strb r6, [r5, #lcr0] ; Tx and Rx buffers set up pop {r5, r6, pc} ; subroutine Transmit ; Puts one byte into the UART for transmitting ; Registers used: ; r5 - scratch register ; r6 - scratch register ; inputs: r0 - byte to transmit ; outputs: none Transmit push {r5, r6, lr} ldr r5, = u1start wait ldrb r6, [r5, #lsr0] ; get status of buffer cmp r6, #0x20 ; buffer empty? beq wait ; spin until buffer is empty strb r0, [r5] pop {r5, r6, pc} CharData dcb "Hello Professor! How are you?", 0 end
So start with a loop. Not too hard to implement. Expand the loop to check if there are any incoming data from any UART to pick up and place in a receive buffer. Expand the loop to check if there are any buffered data that should be sent to any UART - and if that UART is ready to accept more. Expand the loop to scan a keyboard, and if a key is detected store in a receive buffer.
What exact problems do you see with implementing a basic program skeleton and then add features one at a time? All software is created by the creation of individual blocks that are merged into larger and larger programs - or maybe into macro-blocks that are then merged into the program. So it's similar to running a marathon - you do it one step at a time.
Ok, so far I have the following code, but still unable to see any results in serial window uart #1 or #2. I am also unable to type any characters in either of the mentioned windows. so even if the code was incorrect, how do I fix the problem of being able to type characters in the uart windows? I can get the cursor to flash in the windows but it does not receive any texts from the keyboard.
; modified UART code for LPC2104 from Hohl and Hinds, Section 16.2.5 ; The modifications are to use push/pop instead of stmia/ldmdb area uartdemo, code, readonly pinsel0 equ 0xe002C000 ; controls function of pins u1start equ 0xE0010000 ; start of UART1 registers lcr0 equ 0xC ; line control register for UART0 lsr0 equ 0x14 ; line status register for UART0 ramstart equ 0x40000000 ; start of onboard RAM for 2104 stackstart equ 0x40000200 ; start of stack entry start ldr sp, = stackstart ; set up stack pointer bl UARTConfig ; initialize/configure UART0 ; go_again bl Transmit bl send bl go_again ;loop ;ldrb r0, [r1], #1 ; load character, increment address ;cmp r0, #0 ; null terminated? ;blne Transmit ; send character to UART ;bne loop ; continue if not a '0' ;done b done ; otherwise, we are done ; subroutine UARTConfig ; Configures the I/O pins first. ; Then sets up the UART control register. ; Parameters set to 8 bits, no parity, and 1 stop bit. ; Registers used: ; r5 - scratch register ; r6 - scratch register ; inputs: none ; outputs: none UARTConfig push {r5, r6, lr} ldr r5, = pinsel0 ; base address of register ldr r6, [r5] ; get contents bic r6, r6, #0xF0000 ; clear out lower nibble bic r6, r6, #0x0000F ; clear out lower nibble orr r6, r6, #0x50000 ; sets P0.8 and P0.9 orr r6, r6, #0x00005 ; sets P0.0 to Tx0 and P0.1 to Rx0 str r6, [r5] ; r/modify/w back to register ldr r5, = u1start mov r6, #0x83 ; set 8 bits, no parity, 1 stop bit strb r6, [r5, #lcr0] ; write control byte to LCR mov r6, #0x61 ; 9600 baud @ 15MHz VPB clock strb r6, [r5] ; store control byte mov r6, #3 ; set DLAB = 0 strb r6, [r5, #lcr0] ; Tx and Rx buffers set up pop {r5, r6, pc} ; subroutine Transmit ; Puts one byte into the UART for transmitting ; Registers used: ; r5 - scratch register ; r6 - scratch register ; inputs: r0 - byte to transmit ; outputs: none Transmit push {r5, r6, lr} ldr r5, = u1start send ldr r5, = u1start LDRB r6, [r5, #lsr0] tst r0, #0x5f beq wait LDRB r0, [r5] ;LDR r5,=u1start wait ldrb r6, [r5, #lsr0] ; get status of buffer tst r6, #0x20 ; buffer empty? beq wait ; spin until buffer is empty strb r0, [r5] pop {r5, r6, pc} b Transmit end