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Properly map IO and PAD register offsets for QSPI #697

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Merged
merged 3 commits into from
Sep 4, 2025
Merged

Properly map IO and PAD register offsets for QSPI #697

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122daf2
Properly map IO and PAD register offsets for QSPI
lifeisafractal Aug 18, 2025
a30d28f
Use function defines from QSPI definitions
lifeisafractal Aug 20, 2025
6e58bb5
remove 'static' per PR discussion
lifeisafractal Aug 22, 2025
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35 changes: 28 additions & 7 deletions bootloaders/uart/uart_binary.c
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Original file line number Diff line number Diff line change
Expand Up @@ -14,7 +14,7 @@
#endif

// Initialize the GPIO for the LED
void pico_led_init(void) {
static void pico_led_init(void) {
#ifdef PICO_DEFAULT_LED_PIN
// A device like Pico that uses a GPIO for the LED will define PICO_DEFAULT_LED_PIN
// so we can use normal GPIO functionality to turn the led on and off
Expand All @@ -24,23 +24,44 @@ void pico_led_init(void) {
}

// Turn the LED on or off
void pico_set_led(bool led_on) {
static void pico_set_led(bool led_on) {
#if defined(PICO_DEFAULT_LED_PIN)
// Just set the GPIO on or off
gpio_put(PICO_DEFAULT_LED_PIN, led_on);
#endif
}

enum qspi_gpio {
// arbitrarily choose PAD register bank to set the order
QSPI_GPIO_SCLK = 0,
QSPI_GPIO_SD0 = 1,
QSPI_GPIO_SD1 = 2,
QSPI_GPIO_SD2 = 3,
QSPI_GPIO_SD3 = 4,
QSPI_GPIO_SS = 5,
};

// curiously the IO and PAD register banks for the QSPI GPIOs are not in the same order
// This look up table will map the PAD offset to the IO offset for the same pin
static const uint QSPI_GPIO_PAD_TO_IO_OFFSET[] = {
0, // SCLK
2, // SD0
3, // SD1
4, // SD2
5, // SD3
1, // SS
};

// Set function for QSPI GPIO pin
void qspi_gpio_set_function(uint gpio, gpio_function_t fn) {
static void qspi_gpio_set_function(enum qspi_gpio gpio, gpio_function_t fn) {
// Set input enable on, output disable off
hw_write_masked(&pads_qspi_hw->io[gpio],
PADS_QSPI_GPIO_QSPI_SD2_IE_BITS,
PADS_QSPI_GPIO_QSPI_SD2_IE_BITS | PADS_QSPI_GPIO_QSPI_SD2_OD_BITS
);
// Zero all fields apart from fsel; we want this IO to do what the peripheral tells it.
// This doesn't affect e.g. pullup/pulldown, as these are in pad controls.
io_qspi_hw->io[gpio].ctrl = fn << IO_QSPI_GPIO_QSPI_SD2_CTRL_FUNCSEL_LSB;
io_qspi_hw->io[QSPI_GPIO_PAD_TO_IO_OFFSET[gpio]].ctrl = fn << IO_QSPI_GPIO_QSPI_SD2_CTRL_FUNCSEL_LSB;

// Remove pad isolation now that the correct peripheral is in control of the pad
hw_clear_bits(&pads_qspi_hw->io[gpio], PADS_QSPI_GPIO_QSPI_SD2_ISO_BITS);
Expand All @@ -49,9 +70,9 @@ void qspi_gpio_set_function(uint gpio, gpio_function_t fn) {
int main() {
pico_led_init();

// SD2 is QSPI GPIO 3, SD3 is QSPI GPIO 4
qspi_gpio_set_function(3, GPIO_FUNC_UART_AUX);
qspi_gpio_set_function(4, GPIO_FUNC_UART_AUX);
// SD2 is UART0 TX, SD3 is UART0 RX (same as the ROM UART bootloader)
qspi_gpio_set_function(QSPI_GPIO_SD2, GPIO_FUNC_UART_AUX);
qspi_gpio_set_function(QSPI_GPIO_SD3, GPIO_FUNC_UART_AUX);

uart_init(uart0, 1000000);

Expand Down