qemu-arm/uart: Implement uart_rx_chr.

Signed-off-by: Damien George <damien@micropython.org>

ports/qemu-arm/uart.c

@@ -31,14 +31,29 @@
 
 #if defined(QEMU_SOC_STM32)
 
+#define UART_SR_RXNE (1 << 5)
+#define UART_CR1_UE (1 << 13)
+#define UART_CR1_TE (1 << 3)
+#define UART_CR1_RE (1 << 2)
+
 typedef struct _UART_t {
     volatile uint32_t SR;
     volatile uint32_t DR;
+    volatile uint32_t BRR;
+    volatile uint32_t CR1;
 } UART_t;
 
 #define UART0 ((UART_t *)(0x40011000))
 
 void uart_init(void) {
+    UART0->CR1 = UART_CR1_UE | UART_CR1_TE | UART_CR1_RE;
+}
+
+int uart_rx_chr(void) {
+    if (!(UART0->SR & UART_SR_RXNE)) {
+        return UART_RX_NO_CHAR;
+    }
+    return UART0->DR;
 }
 
 void uart_tx_strn(const char *buf, size_t len) {
@@ -50,11 +65,15 @@ void uart_tx_strn(const char *buf, size_t len) {
 #elif defined(QEMU_SOC_NRF51)
 
 typedef struct _UART_t {
-    volatile uint32_t r0[2];
+    volatile uint32_t STARTRX;  // 0x000
+    volatile uint32_t STOPRX;   // 0x004
     volatile uint32_t STARTTX;  // 0x008
-    volatile uint32_t r1[(0x500 - 0x008) / 4 - 1];
+    volatile uint32_t r0[(0x108 - 0x008) / 4 - 1];
+    volatile uint32_t RXDRDY;  // 0x108
+    volatile uint32_t r1[(0x500 - 0x108) / 4 - 1];
     volatile uint32_t ENABLE;   // 0x500
-    volatile uint32_t r2[(0x51c - 0x500) / 4 - 1];
+    volatile uint32_t r2[(0x518 - 0x500) / 4 - 1];
+    volatile uint32_t RXD;      // 0x518
     volatile uint32_t TXD;      // 0x51c
 } UART_t;
 
@@ -62,9 +81,18 @@ typedef struct _UART_t {
 
 void uart_init(void) {
     UART0->ENABLE = 4;
+    UART0->STARTRX = 1;
     UART0->STARTTX = 1;
 }
 
+int uart_rx_chr(void) {
+    if (!UART0->RXDRDY) {
+        return UART_RX_NO_CHAR;
+    }
+    UART0->RXDRDY = 0;
+    return UART0->RXD;
+}
+
 void uart_tx_strn(const char *buf, size_t len) {
     for (size_t i = 0; i < len; ++i) {
         UART0->TXD = buf[i];
@@ -74,6 +102,7 @@ void uart_tx_strn(const char *buf, size_t len) {
 #elif defined(QEMU_SOC_MPS2)
 
 #define UART_STATE_TXFULL (1 << 0)
+#define UART_STATE_RXFULL (1 << 1)
 
 #define UART_CTRL_TX_EN (1 << 0)
 #define UART_CTRL_RX_EN (1 << 1)
@@ -90,7 +119,14 @@ typedef struct _UART_t {
 
 void uart_init(void) {
     UART0->BAUDDIV = 16;
-    UART0->CTRL = UART_CTRL_TX_EN;
+    UART0->CTRL = UART_CTRL_TX_EN | UART_CTRL_RX_EN;
+}
+
+int uart_rx_chr(void) {
+    if (!(UART0->STATE & UART_STATE_RXFULL)) {
+        return UART_RX_NO_CHAR;
+    }
+    return UART0->DATA;
 }
 
 void uart_tx_strn(const char *buf, size_t len) {
@@ -104,7 +140,9 @@ void uart_tx_strn(const char *buf, size_t len) {
 #elif defined(QEMU_SOC_IMX6)
 
 #define UART_UCR1_UARTEN (1 << 0)
+#define UART_UCR2_RXEN (1 << 1)
 #define UART_UCR2_TXEN (1 << 2)
+#define UART_UTS1_RXEMPTY (1 << 5)
 
 typedef struct _UART_t {
     volatile uint32_t URXD; // 0x00
@@ -113,13 +151,22 @@ typedef struct _UART_t {
     volatile uint32_t r1[15];
     volatile uint32_t UCR1; // 0x80
     volatile uint32_t UCR2; // 0x84
+    volatile uint32_t r2[11];
+    volatile uint32_t UTS1; // 0xb4
 } UART_t;
 
 #define UART1 ((UART_t *)(0x02020000))
 
 void uart_init(void) {
     UART1->UCR1 = UART_UCR1_UARTEN;
-    UART1->UCR2 = UART_UCR2_TXEN;
+    UART1->UCR2 = UART_UCR2_TXEN | UART_UCR2_RXEN;
+}
+
+int uart_rx_chr(void) {
+    if (UART1->UTS1 & UART_UTS1_RXEMPTY) {
+        return UART_RX_NO_CHAR;
+    }
+    return UART1->URXD & 0xff;
 }
 
 void uart_tx_strn(const char *buf, size_t len) {

ports/qemu-arm/uart.h

@@ -28,7 +28,11 @@
 
 #include <stddef.h>
 
+// Returned from uart_rx_chr when there are no chars available.
+#define UART_RX_NO_CHAR (-1)
+
 void uart_init(void);
+int uart_rx_chr(void);
 void uart_tx_strn(const char *buf, size_t len);
 
 #endif // MICROPY_INCLUDED_QEMU_ARM_UART_H