initial

vnproglib/c/examples/spi/main.c

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+#include <stdio.h>
+#include <string.h>
+
+/* Include to get access to the VectorNav SPI functions. */
+#include "vn/protocol/spi.h"
+#include "vn/protocol/common.h"
+#include "vn/xplat/thread.h"
+
+int display_error(const char* msg);
+void mockspi_initialize(void);
+void mockspi_writeread(const char* dataOut, size_t dataOutSize, char* dataIn);
+
+int main(void)
+{
+	/* This example walks through using the VectorNav C Library to connect to
+	 * and interact with a mock VectorNav sensor through the Serial Peripheral
+	 * Interaface (SPI). Once you work through and understand the example, you
+	 * may want to try replacing the mock functions with ones that interface
+	 * with your SPI subsystem. */
+
+	char txbuf[0x100];
+	char rxbuf[0x100];
+	size_t bufcmdsize;
+	size_t responseSize;
+	vec3f ypr;
+	char strConversions[50];
+	size_t i;
+
+	mockspi_initialize();
+
+	/* With SPI 'initialize', let's work through reading the current yaw, pitch,
+	 * roll values from the sensor. */
+
+	/* First we must generate the command to query the sensor. */
+	bufcmdsize = sizeof(txbuf);		/* First set this variable to the size of the buffer. */
+	if (VnSpi_genReadYawPitchRoll(
+		txbuf,
+		&bufcmdsize,				/* Pass in the pointer since the function will set this with the length of the command generate. */
+		0,
+		&responseSize) != E_NONE)
+		return display_error("Error generating read yaw, pitch, roll command.\n");
+
+	/* Send out the command over SPI. */
+	mockspi_writeread(
+		txbuf,
+		responseSize,
+		rxbuf);
+
+	/* Now the sensor will have responded with data on this transaction but
+	 * since the sensor only responds on following transaction, we will
+	 * disregard this data. These double transactions can be mitigated by only
+	 * requesting the same data each time or by staggering the the requested
+	 * data in an appropriate order. */
+
+	/* Make sure enough time has passed for the sensor to format the previous response. */
+	VnThread_sleepMs(1);	/* Actual sensor requirement is only 50 us. */
+
+	/* Retransmit so the sensor responds with the previous request. */
+	mockspi_writeread(
+		txbuf,
+		responseSize,
+		rxbuf);
+
+	/* Now parse the received response. */
+	if (VnSpi_parseYawPitchRoll(
+		rxbuf,
+		&ypr) != E_NONE)
+		return display_error("Error parsing yaw, pitch, roll.\n");
+
+	str_vec3f(strConversions, ypr);
+	printf("Current YPR: %s\n", strConversions);
+
+	/* We have now shown how to process one full command transaction which
+	 * requires two SPI transactions because the VectorNav sensor requires a
+	 * short amount of time to ready the response. Now we can optimize this
+	 * transaction squence to utilize this behavior when we are only requesting
+	 * the same data each time. This is illustrated in the for loop below. */
+
+	for (i = 0; i < 25; i++)
+	{
+		/* For this loop, we want to display data at ~10 Hz. */
+		VnThread_sleepMs(100);
+
+		/* Perform a transaction for the same sensor register. */
+		mockspi_writeread(
+			txbuf,
+			responseSize,
+			rxbuf);
+
+		/* Now since the previous command was for the same register, we will
+		 * have valid data and can print/use the results. */
+		if (VnSpi_parseYawPitchRoll(
+			rxbuf,
+			&ypr) != E_NONE)
+			return display_error("Error parsing yaw, pitch, roll.\n");
+
+		str_vec3f(strConversions, ypr);
+		printf("Current YPR: %s\n", strConversions);
+	}
+
+	/* We illustrate how to write settings to the sensor by changing the
+	 * asynchronous data output type. Note that this setting only affects the
+	 * output on the UART ports and has no effect on the SPI ports. It is only
+	 * used for illustration purposes. */
+
+	/* Remember to reset the bufcmdsize variable to let the function know how
+	 * large the provided buffer is. */
+	bufcmdsize = sizeof(txbuf);
+
+	if (VnSpi_genWriteAsyncDataOutputType(
+		txbuf,
+		&bufcmdsize,
+		0,
+		&responseSize,
+		VNYPR) != E_NONE)
+		return display_error("Error generating write async data output type command.\n");
+
+	mockspi_writeread(
+		txbuf,
+		responseSize,
+		rxbuf);
+
+	return 0;
+}
+
+int display_error(const char* msg)
+{
+	printf("%s\n", msg);
+	return -1;
+}
+
+void mockspi_initialize(void)
+{
+	/* Do nothing since we are faking the SPI interface. */
+}
+
+void mockspi_writeread(const char* dataOut, size_t dataOutSize, char* dataIn)
+{
+	/* This function fakes a SPI subsystem for this example. */
+
+	char yprResponse[] = { 0x00, 0x01, 0x08, 0x00, 0xd8, 0x9c, 0xd4, 0x42, 0x44, 0xba, 0x9e, 0x40, 0x4e, 0xe4, 0x8b, 0x40 };
+
+	/* Silence 'unreferenced formal parameters' warning in Visual Studio. */
+	(dataOut);
+	(dataOutSize);
+
+	memcpy(dataIn, yprResponse, sizeof(yprResponse));
+}