GPS: Replace UBX over I2C to NMEA over UART

1 files changed, 155 insertions, 0 deletions

diff --git a/src/fsm/usart.c b/src/fsm/usart.c
new file mode 100644
index 0000000..013c4db
--- /dev/null
+++ b/src/fsm/usart.c
@@ -0,0 +1,155 @@
+/*
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2015 Matthias P. Braendli
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+*/
+
+#include "common.h"
+#include "usart.h"
+#include <stm32f4xx.h>
+#include <stm32f4xx_usart.h>
+#include <stm32f4xx_conf.h>
+#include "FreeRTOS.h"
+#include "task.h"
+#include "queue.h"
+
+// USART 3 on PD8 and PD9
+const uint16_t GPIOD_PIN_USART3_TX = GPIO_Pin_8;
+const uint16_t GPIOD_PIN_USART3_RX = GPIO_Pin_9;
+
+// The ISR writes into this buffer
+static char nmea_sentence[MAX_NMEA_SENTENCE_LEN];
+static int  nmea_sentence_last_written = 0;
+
+// Once a completed NMEA sentence is received in the ISR,
+// it is appended to this queue
+static QueueHandle_t usart_nmea_queue;
+
+void usart_init()
+{
+    usart_nmea_queue = xQueueCreate(15, MAX_NMEA_SENTENCE_LEN);
+    if (usart_nmea_queue == 0) {
+        while(1); /* fatal error */
+    }
+
+    // Setup GPIO D and connect to USART 3
+    RCC_APB1PeriphClockCmd(RCC_APB1Periph_USART3, ENABLE);
+    RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOD, ENABLE);
+
+    GPIO_InitTypeDef GPIO_InitStruct;
+    GPIO_InitStruct.GPIO_Pin = GPIOD_PIN_USART3_RX | GPIOD_PIN_USART3_TX;
+    GPIO_InitStruct.GPIO_Mode = GPIO_Mode_AF;
+    GPIO_InitStruct.GPIO_Speed = GPIO_Speed_50MHz;
+    GPIO_InitStruct.GPIO_OType = GPIO_OType_PP;
+    GPIO_InitStruct.GPIO_PuPd = GPIO_PuPd_UP;
+    GPIO_Init(GPIOD, &GPIO_InitStruct);
+
+    GPIO_PinAFConfig(GPIOD, GPIO_PinSource8, GPIO_AF_USART3);
+    GPIO_PinAFConfig(GPIOD, GPIO_PinSource9, GPIO_AF_USART3);
+
+    // Setup USART3 for 9600,8,N,1
+
+    USART_InitTypeDef USART_InitStruct;
+    USART_InitStruct.USART_BaudRate = 9600;
+    USART_InitStruct.USART_WordLength = USART_WordLength_8b;
+    USART_InitStruct.USART_StopBits = USART_StopBits_1;
+    USART_InitStruct.USART_Parity = USART_Parity_No;
+    USART_InitStruct.USART_HardwareFlowControl = USART_HardwareFlowControl_None;
+    USART_InitStruct.USART_Mode = USART_Mode_Tx | USART_Mode_Rx;
+    USART_Init(USART3, &USART_InitStruct);
+
+
+    // enable the USART3 receive interrupt
+    USART_ITConfig(USART3, USART_IT_RXNE, ENABLE);
+
+    NVIC_InitTypeDef NVIC_InitStructure;
+    NVIC_InitStructure.NVIC_IRQChannel = USART3_IRQn;
+    NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 6;
+    NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0;
+    NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
+    NVIC_Init(&NVIC_InitStructure);
+
+    NVIC_SetPriority(USART3_IRQn, 6);
+
+    // finally this enables the complete USART3 peripheral
+    USART_Cmd(USART3, ENABLE);
+}
+
+void usart_puts(const char* str)
+{
+    while(*str) {
+        // wait until data register is empty
+        while ( !(USART3->SR & 0x00000040) );
+        USART_SendData(USART3, *str);
+        str++;
+    }
+}
+
+int usart_get_nmea_sentence(char* nmea)
+{
+    return xQueueReceive(usart_nmea_queue, nmea, portMAX_DELAY);
+}
+
+
+static void usart_clear_nmea_buffer(void)
+{
+    for (int i = 0; i < MAX_NMEA_SENTENCE_LEN; i++) {
+        nmea_sentence[i] = '\0';
+    }
+    nmea_sentence_last_written = 0;
+}
+
+void USART3_IRQHandler(void)
+{
+    if (USART_GetITStatus(USART3, USART_IT_RXNE)) {
+        char t = USART3->DR;
+
+        if (nmea_sentence_last_written == 0) {
+            if (t == '$') {
+                // Likely new start of sentence
+                nmea_sentence[nmea_sentence_last_written] = t;
+                nmea_sentence_last_written++;
+            }
+        }
+        else if (nmea_sentence_last_written < MAX_NMEA_SENTENCE_LEN) {
+            nmea_sentence[nmea_sentence_last_written] = t;
+            nmea_sentence_last_written++;
+
+            if (t == '\n') {
+                int success = xQueueSendToBackFromISR(
+                        usart_nmea_queue,
+                        nmea_sentence,
+                        NULL);
+
+                if (success == pdFALSE) {
+                    trigger_fault(FAULT_SOURCE_USART);
+                }
+
+                usart_clear_nmea_buffer();
+            }
+        }
+        else {
+            // Buffer overrun without a meaningful NMEA message.
+            usart_clear_nmea_buffer();
+        }
+    }
+}
+