From 8e161664bb76e6dff7080181cb8ce17bc55e1ba6 Mon Sep 17 00:00:00 2001
From: Byron Lathi <bslathi19@gmail.com>
Date: Mon, 14 Mar 2022 16:48:24 -0500
Subject: [PATCH] Add uart_rxb

Once you receive a uart interrupt you can call this function to get the
received character.
---
 sw/irq.c  | 6 ++++++
 sw/uart.h | 2 ++
 sw/uart.s | 9 +++++++--
 3 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/sw/irq.c b/sw/irq.c
index a7f7287..3608879 100644
--- a/sw/irq.c
+++ b/sw/irq.c
@@ -2,12 +2,14 @@
 #include <stdint.h>
 
 #include "interrupt.h"
+#include "uart.h"
 
 // This is defined in main.c
 void puts(const char* s);
 
 void handle_irq() {
     uint8_t status;
+    char c;
 
     puts("Interrupt Detected!\n");
 
@@ -19,6 +21,10 @@ void handle_irq() {
     }
     if (status & UART) {
         puts("UART Interrupt!\n");
+        c = uart_rxb();
+        puts("Received: ");
+        puts(&c);
+        puts("\n");
         irq_set_status(status & ~UART);
     }
 }
\ No newline at end of file
diff --git a/sw/uart.h b/sw/uart.h
index c96b48c..e8f06db 100644
--- a/sw/uart.h
+++ b/sw/uart.h
@@ -6,6 +6,8 @@
 void uart_txb(uint8_t val);
 void uart_txb_block(uint8_t val);
 
+uint8_t uart_rxb();
+
 uint8_t uart_status();
 
 #endif
\ No newline at end of file
diff --git a/sw/uart.s b/sw/uart.s
index 80b5563..dd23778 100644
--- a/sw/uart.s
+++ b/sw/uart.s
@@ -2,8 +2,8 @@
 
 .importzp sp, sreg
 
-.export _uart_txb
-.export _uart_txb_block
+.export _uart_txb, _uart_txb_block
+.export _uart_rxb
 .export _uart_status
 
 .autoimport	on
@@ -23,6 +23,11 @@ _uart_txb_block:
         bne @1
         rts
 
+_uart_rxb:
+        lda UART_RXB        ; Read value
+        ldx #$00
+        rts
+
 _uart_status:
         lda UART_STATUS
         ldx #$00