1 files changed, 92 insertions, 0 deletions
diff --git a/src/rp2040/serial.c b/src/rp2040/serial.c
new file mode 100644
index 00000000..abfdcb8b
--- /dev/null
+++ b/src/rp2040/serial.c
@@ -0,0 +1,92 @@
+// rp2040 serial
+//
+// Copyright (C) 2021  Kevin O'Connor <kevin@koconnor.net>
+//
+// This file may be distributed under the terms of the GNU GPLv3 license.
+
+#include <stdint.h> // uint32_t
+#include "autoconf.h" // CONFIG_SERIAL
+#include "board/armcm_boot.h" // armcm_enable_irq
+#include "board/irq.h" // irq_save
+#include "board/serial_irq.h" // serial_rx_data
+#include "hardware/structs/resets.h" // RESETS_RESET_UART0_BITS
+#include "hardware/structs/uart.h" // UART0_BASE
+#include "internal.h" // UART0_IRQn
+#include "sched.h" // DECL_INIT
+
+#define UARTx uart0_hw
+#define UARTx_IRQn UART0_IRQ_IRQn
+#define GPIO_Rx 1
+#define GPIO_Tx 0
+
+// Write tx bytes to the serial port
+static void
+kick_tx(void)
+{
+    for (;;) {
+        if (UARTx->fr & UART_UARTFR_TXFF_BITS) {
+            // Output fifo full - enable tx irq
+            UARTx->imsc = (UART_UARTIMSC_RXIM_BITS | UART_UARTIMSC_RTIM_BITS
+                           | UART_UARTIMSC_TXIM_BITS);
+            break;
+        }
+        uint8_t data;
+        int ret = serial_get_tx_byte(&data);
+        if (ret) {
+            // No more data to send - disable tx irq
+            UARTx->imsc = UART_UARTIMSC_RXIM_BITS | UART_UARTIMSC_RTIM_BITS;
+            break;
+        }
+        UARTx->dr = data;
+    }
+}
+
+void
+UARTx_IRQHandler(void)
+{
+    uint32_t mis = UARTx->mis;
+    if (mis & (UART_UARTMIS_RXMIS_BITS | UART_UARTMIS_RTMIS_BITS)) {
+        do {
+            serial_rx_byte(UARTx->dr);
+        } while (!(UARTx->fr & UART_UARTFR_RXFE_BITS));
+    } else if (mis & UART_UARTMIS_TXMIS_BITS) {
+        kick_tx();
+    }
+}
+
+void
+serial_enable_tx_irq(void)
+{
+    if (!(UARTx->fr & UART_UARTFR_TXFF_BITS)) {
+        irqstatus_t flag = irq_save();
+        kick_tx();
+        irq_restore(flag);
+    }
+}
+
+void
+serial_init(void)
+{
+    enable_pclock(RESETS_RESET_UART0_BITS);
+
+    // Setup baud
+    uint32_t pclk = get_pclock_frequency(RESETS_RESET_UART0_BITS);
+    uint32_t div = DIV_ROUND_CLOSEST(pclk * 4, CONFIG_SERIAL_BAUD);
+    UARTx->ibrd = div >> 6;
+    UARTx->fbrd = div & 0x3f;
+
+    // Enable fifo, set 8N1
+    UARTx->lcr_h = UART_UARTLCR_H_FEN_BITS | UART_UARTLCR_H_WLEN_BITS;
+    UARTx->ifls = 0;
+    UARTx->cr = (UART_UARTCR_RXE_BITS | UART_UARTCR_TXE_BITS
+                 | UART_UARTCR_UARTEN_BITS);
+
+    // Setup pins
+    gpio_peripheral(GPIO_Rx, 2, 1);
+    gpio_peripheral(GPIO_Tx, 2, 0);
+
+    // Enable receive irq
+    armcm_enable_irq(UARTx_IRQHandler, UARTx_IRQn, 0);
+    UARTx->imsc = UART_UARTIMSC_RXIM_BITS | UART_UARTIMSC_RTIM_BITS;
+}
+DECL_INIT(serial_init);