Clarify GPIO read and write macros
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@ -117,6 +117,20 @@ typedef void (* gpio_callback_t)(uint8_t port, uint8_t pin);
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/** \brief Set pins with PIN_MASK of port with PORT_BASE to value.
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* \param PORT_BASE GPIO Port register offset
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* \param PIN_MASK Pin number mask. Pin 0: 0x01, Pin 1: 0x02 ... Pin 7: 0x80
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* \param value The new value to write to the register. Only pins specified
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* by PIN_MASK will be set.
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*
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* \note The outcome of this macro invocation will be to write to the register
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* a new value for multiple pins. For that reason, the value argument cannot be
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* a simple 0 or 1. Instead, it must be the value corresponding to the pins that
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* you wish to set.
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*
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* Thus, if you only want to set a single pin (e.g. pin 2), do \e not pass 1,
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* but you must pass 0x04 instead (1 << 2). This may seem counter-intuitive at
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* first glance, but it allows a single invocation of this macro to set
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* multiple pins in one go if so desired. For example, you can set pins 3 and 1
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* and the same time clear pins 2 and 0. To do so, pass 0x0F as the PIN_MASK
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* and then use 0x0A as the value ((1 << 3) | (1 << 1) for pins 3 and 1)
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*/
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#define GPIO_WRITE_PIN(PORT_BASE, PIN_MASK, value) \
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do { REG(((PORT_BASE) | GPIO_DATA) + ((PIN_MASK) << 2)) = (value); } while(0)
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@ -124,6 +138,12 @@ typedef void (* gpio_callback_t)(uint8_t port, uint8_t pin);
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/** \brief Read pins with PIN_MASK of port with PORT_BASE.
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* \param PORT_BASE GPIO Port register offset
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* \param PIN_MASK Pin number mask. Pin 0: 0x01, Pin 1: 0x02 ... Pin 7: 0x80
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* \return The value of the pins specified by PIN_MASK
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*
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* This macro will \e not return 0 or 1. Instead, it will return the values of
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* the pins specified by PIN_MASK ORd together. Thus, if you pass 0xC3
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* (0x80 | 0x40 | 0x02 | 0x01) as the PIN_MASK and pins 7 and 0 are high,
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* the macro will return 0x81.
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*/
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#define GPIO_READ_PIN(PORT_BASE, PIN_MASK) \
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REG(((PORT_BASE) | GPIO_DATA) + ((PIN_MASK) << 2))
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@ -261,7 +281,7 @@ typedef void (* gpio_callback_t)(uint8_t port, uint8_t pin);
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/**
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* \brief Converts a pin number to a pin mask
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* \param The pin number in the range [0..7]
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* \param PIN The pin number in the range [0..7]
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* \return A pin mask which can be used as the PIN_MASK argument of the macros
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* in this category
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*/
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@ -269,7 +289,7 @@ typedef void (* gpio_callback_t)(uint8_t port, uint8_t pin);
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/**
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* \brief Converts a port number to the port base address
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* \param The port number in the range 0 - 3. Likely GPIO_X_NUM.
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* \param PORT The port number in the range 0 - 3. Likely GPIO_X_NUM.
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* \return The base address for the registers corresponding to that port
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* number.
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*/
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