Implement batch transmission

ChangeLog.md

@@ -13,6 +13,9 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 ### Changed
 
 ### Added
+- Added support for caching readings in RAM and sending in batches.
+This currently only works on the EnviroDIY/Monitor My Watershed Publisher.
+Thank you to [Thomas Watson](https://github.com/tpwrules) for this work.
 
 ### Removed
 

src/LogBuffer.cpp

@@ -0,0 +1,102 @@
+/**
+ * @file LogBuffer.cpp
+ * @copyright 2023 Thomas Watson
+ * Part of the EnviroDIY ModularSensors library for Arduino
+ * @author Thomas Watson <twatson52@icloud.com>
+ *
+ * @brief Implements the LogBuffer class.
+ *
+ * This class buffers logged timestamps and variable values for transmission.
+ */
+#include "LogBuffer.h"
+
+#include <string.h>
+
+// Constructor
+LogBuffer::LogBuffer() {}
+// Destructor
+LogBuffer::~LogBuffer() {}
+
+void LogBuffer::setNumVariables(uint8_t numVariables_) {
+    // each record is one uint32_t to hold the timestamp, plus N floats to hold
+    // each variable's value
+    recordSize   = sizeof(uint32_t) + sizeof(float) * numVariables_;
+    numVariables = numVariables_;
+
+    // this scrambles all the data in the buffer so clear it out
+    clear();
+}
+
+void LogBuffer::clear(void) {
+    // clear out the buffer
+    numRecords      = 0;
+    dataBufferTail  = 0;
+    dataBufferHead  = 0;
+    _bufferOverflow = false;
+}
+
+uint8_t LogBuffer::getNumVariables(void) {
+    return numVariables;
+}
+
+int LogBuffer::getNumRecords(void) {
+    return numRecords;
+}
+
+uint8_t LogBuffer::getPercentFull(void) {
+    uint32_t bytesFull  = (uint32_t)numRecords * (uint32_t)recordSize;
+    uint32_t bytesTotal = MS_LOG_DATA_BUFFER_SIZE;
+
+    return (uint8_t)((bytesFull * (uint32_t)100) / bytesTotal);
+}
+
+int LogBuffer::addRecord(uint32_t timestamp) {
+    // check how many records currently exist
+    int record = numRecords;
+    // compute position of the new record's timestamp in the buffer
+    // (the timestamp is the first data in the record)
+    size_t pos = record * recordSize;
+    // verify we have sufficient space for the record and bail if not
+    if (MS_LOG_DATA_BUFFER_SIZE - pos < recordSize) { return -1; }
+
+    // write the timestamp to the record
+    memcpy(static_cast<void*>(&dataBuffer[pos]), static_cast<void*>(&timestamp),
+           sizeof(uint32_t));
+    numRecords += 1;  // just added another record
+
+    // return the index of the record number just created
+    return record;
+}
+
+void LogBuffer::setRecordValue(int record, uint8_t variable, float value) {
+    // compute position of this value in the buffer
+    size_t pos = record * recordSize + sizeof(uint32_t) +
+        variable * sizeof(float);
+
+    // write the value to the record
+    memcpy(static_cast<void*>(&dataBuffer[pos]), static_cast<void*>(&value),
+           sizeof(float));
+}
+
+uint32_t LogBuffer::getRecordTimestamp(int record) {
+    // read the timestamp from the record (which is the first data in it)
+    uint32_t timestamp;
+    memcpy(static_cast<void*>(&timestamp),
+           static_cast<void*>(&dataBuffer[record * recordSize]),
+           sizeof(uint32_t));
+
+    return timestamp;
+}
+
+float LogBuffer::getRecordValue(int record, uint8_t variable) {
+    // compute position of this value in the buffer
+    size_t pos = record * recordSize + sizeof(uint32_t) +
+        variable * sizeof(float);
+
+    // read the value from the record
+    float value;
+    memcpy(static_cast<void*>(&value), static_cast<void*>(&dataBuffer[pos]),
+           sizeof(float));
+
+    return value;
+}

src/LogBuffer.h

@@ -0,0 +1,161 @@
+/**
+ * @file LogBuffer.cpp
+ * @copyright 2023 Thomas Watson
+ * Part of the EnviroDIY ModularSensors library for Arduino
+ * @author Thomas Watson <twatson52@icloud.com>
+ *
+ * @brief Implements the LogBuffer class.
+ *
+ * This class buffers logged timestamps and variable values for transmission.
+ */
+
+// Header Guards
+#ifndef SRC_LOGBUFFER_H_
+#define SRC_LOGBUFFER_H_
+
+#ifndef MS_LOG_DATA_BUFFER_SIZE
+#ifdef ARDUINO_AVR_MEGA2560
+#define MS_LOG_DATA_BUFFER_SIZE 2048
+#else
+/**
+ * @brief Log Data Buffer
+ *
+ * This determines how much RAM is reserved to buffer log records before
+ * transmission. Each record consumes 4 bytes for the timestamp plus 4 bytes
+ * for each logged variable. Increasing this value too far can crash the
+ * device! The number of log records buffered is controlled by sendEveryX.
+ *
+ * This can be changed by setting the build flag MS_LOG_DATA_BUFFER_SIZE when
+ * compiling. 8192 bytes is a safe value for the Mayfly 1.1 with six variables.
+ */
+#define MS_LOG_DATA_BUFFER_SIZE 8192
+#endif
+#endif
+
+#include <stddef.h>
+#include <inttypes.h>
+
+/**
+ * @brief This class buffers logged timestamps and variable values for
+ * transmission. The log is divided into a number of records. Each record
+ * stores the timestamp of the record as a uint32_t, then the value of each
+ * variable as a float at that time.
+ */
+class LogBuffer {
+ public:
+    /**
+     * @brief Constructs a new empty buffer which stores no variables or values.
+     */
+    LogBuffer();
+    /**
+     * @brief Destroys the buffer.
+     */
+    virtual ~LogBuffer();
+
+    /**
+     * @brief Sets the number of variables the buffer will store in each record.
+     * Clears the buffer as a side effect.
+     *
+     * @param numVariables_  The number of variables to store.
+     */
+    void setNumVariables(uint8_t numVariables_);
+
+    /**
+     * @brief Gets the number of variables that will be stored in each record.
+     *
+     * @return The variable count.
+     */
+    uint8_t getNumVariables(void);
+
+    /**
+     * @brief Clears all records from the log.
+     */
+    void clear(void);
+
+    /**
+     * @brief Gets the number of records currently in the log.
+     *
+     * @return The number of records.
+     */
+    int getNumRecords(void);
+
+    /**
+     * @brief Computes the percentage full of the buffer.
+     *
+     * @return The current percent full.
+     */
+    uint8_t getPercentFull(void);
+
+    /**
+     * @brief Adds a new record with the given timestamp.
+     *
+     * @param timestamp  The timestamp
+     *
+     * @return Index of the new record, or -1 if there was no space.
+     */
+    int addRecord(uint32_t timestamp);
+
+    /**
+     * @brief Sets the value of a particular variable in a particular record.
+     *
+     * @param record    The record
+     * @param variable  The variable
+     * @param value     The value
+     */
+    void setRecordValue(int record, uint8_t variable, float value);
+
+    /**
+     * @brief Gets the timestamp of a particular record.
+     *
+     * @param record  The record
+     *
+     * @return The record's timestamp.
+     */
+    uint32_t getRecordTimestamp(int record);
+
+    /**
+     * @brief Gets the value of a particular variable in a particular record.
+     *
+     * @param record    The record
+     * @param variable  The variable
+     *
+     * @return The variable's value.
+     */
+    float getRecordValue(int record, uint8_t variable);
+
+ protected:
+    /**
+     * @brief Buffer which stores the log data.
+     */
+    uint8_t dataBuffer[MS_LOG_DATA_BUFFER_SIZE];
+
+    /**
+     * @brief Index of buffer head.
+     */
+    uint16_t dataBufferTail;
+    /**
+     * @brief Index of buffer tail.
+     */
+    uint16_t dataBufferHead;
+    /**
+     * @brief The buffer overflow status
+     */
+    bool _bufferOverflow = false;
+
+    /**
+     * @brief Number of records currently in the buffer.
+     */
+    int numRecords;
+
+    /**
+     * @brief Size in bytes of each record in the buffer.
+     */
+    size_t recordSize;
+
+    /**
+     * @brief Number of variables stored in each record in the buffer.
+     */
+    uint8_t numVariables;
+};
+
+#endif  // SRC_LOGBUFFER_H_