diff options
Diffstat (limited to 'uart.s')
| -rw-r--r-- | uart.s | 95 |
1 files changed, 34 insertions, 61 deletions
@@ -2,86 +2,59 @@ .cpu cortex-m0plus .thumb -.equ RESETS_BASE, 0x4000c000 +.equ RESETS_BASE, 0x4000c000 .equ RESET_OFST, 0x0 .equ RESET_DONE_OFST, 0x8 -.equ CLOCKS_BASE, 0x40008000 -.equ CLK_REF_CTRL_OFST, 0x30 -.equ CLK_SYS_CTRL_OFST, 0x3c -.equ CLK_PERI_CTRL_OFST, 0x48 - -.equ UART0_BASE, 0x40034000 -.equ UARTDR_OFST, 0x00 -.equ UARTFR_OFST, 0x18 -.equ UARTIBRD_OFST, 0x24 -.equ UARTFBRD_OFST, 0x28 -.equ UARTLCR_H_OFST, 0x2c -.equ UARTCR_OFST, 0x30 - .equ IO_BANK0_BASE, 0x40014000 .equ GPIO0_CTRL_OFST, 0x04 .equ GPIO1_CTRL_OFST, 0x0c +.equ UART0_BASE, 0x40034000 +.equ UARTDR_OFST, 0x00 +.equ UARTFR_OFST, 0x18 +.equ UARTIBRD_OFST, 0x24 +.equ UARTFBRD_OFST, 0x28 +.equ UARTLCR_H_OFST, 0x2c +.equ UARTCR_OFST, 0x30 + .equ ATOMIC_SET, 0x2000 -.equ ATOMIC_CLEAR, 0x3000 +.equ ATOMIC_CLEAR, 0x3000 .type setup_uart, %function .global setup_uart setup_uart: - // Enable clk_peri - movs r0, 0x1 // set enable bit (0x1 << 11) - lsls r0, 11 - movs r1, 0x4 // use xosc (=0x4 << 5) as clk_ref source - lsls r1, 5 - orrs r0, r1 - ldr r1, =CLOCKS_BASE - str r0, [r1, CLK_PERI_CTRL_OFST] - - // Reset UART0 - movs r0, 1 - lsls r0, r0, 22 // UART0 is bit 22 - - // Assert the reset - ldr r1, =(RESETS_BASE + ATOMIC_SET) - str r0, [r1, RESET_OFST] - - // Deassert the reset + // Deassert reset ldr r1, =(RESETS_BASE + ATOMIC_CLEAR) + movs r0, 0b1 // UART0 + lsls r0, 22 str r0, [r1, RESET_OFST] - - // Check if reset done ldr r1, =RESETS_BASE 1: ldr r2, [r1, RESET_DONE_OFST] - tst r0, r2 + tst r2, r0 beq 1b - // Configure GPIO 0 and 1 as UART0 + // Configure and enable + ldr r1, =UART0_BASE + movs r0, 6 + str r0, [r1, UARTIBRD_OFST] + movs r0, 33 + str r0, [r1, UARTFBRD_OFST] + movs r0, 0b111 << 4 // 0b11 = word len 8 bits, 0b1 = FIFO enabled + str r0, [r1, UARTLCR_H_OFST] + ldr r1, =(UART0_BASE + ATOMIC_SET) + movs r0, 0b1 // UART enable + str r0, [r1, UARTCR_OFST] + + // Configure GPIO 0 and 1 as TX and RX ldr r1, =IO_BANK0_BASE - movs r0, 2 // UART function = 2 + movs r0, 2 // UART function str r0, [r1, GPIO0_CTRL_OFST] str r0, [r1, GPIO1_CTRL_OFST] - // Set the baud rate divisors - movs r0, 6 // integer baud rate = 6 - ldr r0, [r1, UARTIBRD_OFST] - movs r0, 33 // fractional baud rate = 33 - ldr r0, [r1, UARTFBRD_OFST] - - // Enable the FIFOs and set the format - movs r0, 0x70 // word len 8 bits (bits 6:5 = 0b11), bit 4 (FIFO en) - str r0, [r1, UARTLCR_H_OFST] - - // Set enable bits in the control register - ldr r1, =UART0_BASE - movs r0, 0x3 - lsls r0, 8 // set bits 8 and 9 (TX and RX enable) - adds r0, 0x1 // set bit 0 (UART enable) - str r0, [r1, UARTCR_OFST] - bx lr .type uart_send, %function @@ -89,11 +62,11 @@ setup_uart: uart_send: ldr r1, =UART0_BASE -poll_TXFF: +1: ldr r2, [r1, UARTFR_OFST] - movs r3, 0x20 // bit 5 (TX FIFO full) + movs r3, 0b1 << 5 // TX FIFO full tst r2, r3 - bne poll_TXFF + bne 1b movs r2, 0xff ands r0, r2 str r0, [r1, UARTDR_OFST] @@ -104,10 +77,10 @@ poll_TXFF: uart_recv: ldr r1, =UART0_BASE -poll_RXFE: +1: ldr r2, [r1, UARTFR_OFST] - movs r3, 0x10 // bit 4 (RX FIFO empty) + movs r3, 0b1 << 4 // RX FIFO empty tst r2, r3 - bne poll_RXFE + bne 1b ldr r0, [r1, UARTDR_OFST] bx lr |