From c4678339908e413cbc6751cf863267807acafc85 Mon Sep 17 00:00:00 2001
From: Fredrik Thulin <fredrik@thulin.net>
Date: Sun, 28 Jun 2015 16:30:08 +0200
Subject: Enable dual USART output functionality.

In other words, enable the USART connected to the serial port on
the Raspberry Pi GPIO header.

Sending a newline to either USART directs the generated entropy
to that USART.
---
 src/entropy/main.c | 40 +++++++++++++++++++++++++++++++++-------
 1 file changed, 33 insertions(+), 7 deletions(-)

(limited to 'src/entropy/main.c')

diff --git a/src/entropy/main.c b/src/entropy/main.c
index e29e00c..f7663f5 100644
--- a/src/entropy/main.c
+++ b/src/entropy/main.c
@@ -42,6 +42,7 @@
 
 extern DMA_HandleTypeDef hdma_tim;
 
+UART_HandleTypeDef *huart;
 __IO ITStatus UartReady = RESET;
 
 static union {
@@ -79,6 +80,7 @@ inline uint32_t get_one_bit(void) __attribute__((__always_inline__));
 volatile uint32_t *restart_DMA(void);
 inline volatile uint32_t *get_DMA_read_buf(void);
 inline uint32_t safe_get_counter(volatile uint32_t *dmabuf, const uint32_t dmabuf_idx);
+void check_uart_rx(UART_HandleTypeDef *this);
 /* static void Error_Handler(void); */
 
 
@@ -86,7 +88,7 @@ inline uint32_t safe_get_counter(volatile uint32_t *dmabuf, const uint32_t dmabu
 int
 main()
 {
-  uint32_t count = 0, send_bytes, idx = 255, send_sync_bytes_in = 0, i;
+  uint32_t count = 0, send_bytes, idx = 255, send_sync_bytes_in = 0, i, timeout;
   uint32_t mode = MODE_ENTROPY;
 
   /* Initialize buffers */
@@ -101,6 +103,8 @@ main()
   restart_DMA();
   restart_DMA();
 
+  huart = &huart1;
+
   /* Toggle GREEN LED to show we've initialized */
   {
     for (i = 0; i < 10; i++) {
@@ -144,7 +148,8 @@ main()
       }
 
     /* Send buf on UART (non blocking interrupt driven send). */
-    if (HAL_UART_Transmit_IT(&huart1, (uint8_t *) buf.rnd + idx, (uint16_t) send_bytes) == HAL_OK) {
+    UartReady = RESET;
+    if (HAL_UART_Transmit_IT(huart, (uint8_t *) buf.rnd + idx, (uint16_t) send_bytes) == HAL_OK) {
 
       if (mode == MODE_ENTROPY) {
 	/* Flip-flop idx between the value 0 and the value BYTES_PER_CHUNK.
@@ -155,15 +160,21 @@ main()
 	get_entropy32(send_bytes / 4, idx / 4);
       }
 
-      while (UartReady != SET) { ; }
-      UartReady = RESET;
-    } else {
-      /* Turn on RED LED for one second */
+      timeout = 0xffff;
+      while (UartReady != SET && timeout) { timeout--; }
+    }
+
+    if (UartReady != SET) {
+      /* Failed to send, turn on RED LED for one second */
       HAL_GPIO_WritePin(LED_PORT, LED_RED, GPIO_PIN_SET);
       HAL_Delay(1000);
       HAL_GPIO_WritePin(LED_PORT, LED_RED, GPIO_PIN_RESET);
     }
 
+    /* Check for UART change request */
+    check_uart_rx(&huart1);
+    check_uart_rx(&huart2);
+
     count++;
   }
 
@@ -347,12 +358,27 @@ inline uint32_t safe_get_counter(volatile uint32_t *dmabuf, const uint32_t dmabu
 /* UART transmit complete callback */
 void HAL_UART_TxCpltCallback(UART_HandleTypeDef *UH)
 {
-  if (UH->Instance == USART1) {
+  if ((UH->Instance == USART1 && huart->Instance == USART1) ||
+      (UH->Instance == USART2 && huart->Instance == USART2)) {
     /* Signal UART transmit complete to the code in the main loop. */
     UartReady = SET;
   }
 }
 
+/*
+ * If a newline is received on UART1 or UART2, redirect output to that UART.
+ */
+void check_uart_rx(UART_HandleTypeDef *this) {
+  uint8_t rx = 0;
+  if (HAL_UART_Receive(this, &rx, 1, 0) == HAL_OK) {
+    if (rx == '\n') {
+      huart = this;
+      /* Signal UART transmit complete to the code in the main loop. */
+      UartReady = SET;
+    }
+  }
+}
+
 /**
  * @brief  This function is executed in case of error occurrence.
  * @param  None
-- 
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