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+/** \file hdr_gpio_masked_access.h
+ * \brief Header for GPIO masked access in LPC11xx
+ * \details This header contains definitions necessary for using GPIO masked
+ * access feature of LPC11xx chips. GPIO masked access gives you the ability to
+ * set the state of single GPIO pin (or group of pins) without affecting other
+ * pins of the same port, avoiding possible read-modify-store problems. It is
+ * also possible to use GPIO masked access to get the state of single GPIO pin
+ * (or group of pins) without any masking (single read operation).
+ *
+ * To use this mechanism in an convenient way add three definitions to your
+ * code (in the example PIO1_5 (port 1, pin 5) is used):
+ * - #define SOMETHING_GPIO LPC_GPIO1 // GPIO port of the pin
+ * - #define SOMETHING_pin 5 // number of the pin
+ * - #define SOMETHING (1 << SOMETHING_pin) // bit mask
+ *
+ * Then you can define a GPIO masked access "variable" using the macros from
+ * this header:
+ * - #define SOMETHING_gma gpio_masked_access_t GPIO_MASKED_ACCESS(SOMETHING_GPIO, SOMETHING_pin)
+ *
+ * Changing the state of the pin is then very simple:
+ * - SOMETHING_gma = 0;			// pin state == 0
+ * - SOMETHING_gma = SOMETHING;	// pin state == 1
+ *
+ * To set pin state to 0 you can actually write any number that has binary 0 on
+ * SOMETHING_pin bit, so these are equivalent:
+ * - SOMETHING_gma = 0;
+ * - SOMETHING_gma = ANYTHING & ~(SOMETHING);
+ * - SOMETHING_gma = 0xFFFFFFFF & ~(SOMETHING);
+ * - ...
+ *
+ * The same is true for setting pin state to 1, so these are also equivalent:
+ * - SOMETHING_gma = SOMETHING;
+ * - SOMETHING_gma = SOMETHING | ANYTHING;
+ * - SOMETHING_gma = 0xFFFFFFFF;
+ * - ...
+ *
+ * You can also get the state of the pin by reading this "variable":
+ * - uint32_t state_of_pin = SOMETHING_gma; // if pin state == 0, state_of_pin == 0, otherwise state_of_pin == SOMETHING
+ *
+ * \author Freddie Chopin, http://www.freddiechopin.info/
+ * \date 2012-01-08
+ */
+
+/******************************************************************************
+* chip: LPC11xx
+* compiler: arm-none-eabi-gcc (Sourcery CodeBench Lite 2011.09-69) 4.6.1
+******************************************************************************/
+
+#ifndef HDR_GPIO_MASKED_ACCESS_H_
+#define HDR_GPIO_MASKED_ACCESS_H_
+
+#include <stdint.h>
+
+/*
++=============================================================================+
+| strange variables
++=============================================================================+
+*/
+
+/// GPIO masked access "variable" type
+#define gpio_masked_access_t				*(volatile uint32_t*)
+
+/*
++=============================================================================+
+| macros
++=============================================================================+
+*/
+
+/// macro used to calculate the address on the bus that is used to access selected pin
+#define GPIO_MASKED_ACCESS(gpio, pin)		((uint32_t)gpio + (1 << (pin + 2)))
+
+/******************************************************************************
+* END OF FILE
+******************************************************************************/
+#endif /* HDR_GPIO_MASKED_ACCESS_H_ */