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Fix: Update SPI PIO initialization to use 64-bit masks for RP2350B #727

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Fix: Update SPI PIO initialization to use 64-bit masks for RP2350B #727

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0d54450
Update SPI PIO initialization to use 64-bit masks for rp2350b variant
viralpatel9 Dec 17, 2025
a17bb65
Fix spi loopback example to work with any pin
peterharperuk Dec 17, 2025
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1 change: 1 addition & 0 deletions pio/spi/pio_spi.h
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Original file line number Diff line number Diff line change
Expand Up @@ -13,6 +13,7 @@ typedef struct pio_spi_inst {
PIO pio;
uint sm;
uint cs_pin;
uint offset;
} pio_spi_inst_t;

void pio_spi_write8_blocking(const pio_spi_inst_t *spi, const uint8_t *src, size_t len);
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12 changes: 6 additions & 6 deletions pio/spi/spi.pio
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Expand Up @@ -55,8 +55,8 @@ static inline void pio_spi_init(PIO pio, uint sm, uint prog_offs, uint n_bits,
sm_config_set_clkdiv(&c, clkdiv);

// MOSI, SCK output are low, MISO is input
pio_sm_set_pins_with_mask(pio, sm, 0, (1u << pin_sck) | (1u << pin_mosi));
pio_sm_set_pindirs_with_mask(pio, sm, (1u << pin_sck) | (1u << pin_mosi), (1u << pin_sck) | (1u << pin_mosi) | (1u << pin_miso));
pio_sm_set_pins_with_mask64(pio, sm, 0, (1ull << pin_sck) | (1ull << pin_mosi));
pio_sm_set_pindirs_with_mask64(pio, sm, (1ull << pin_sck) | (1ull << pin_mosi), (1ull << pin_sck) | (1ull << pin_mosi) | (1ull << pin_miso));
pio_gpio_init(pio, pin_mosi);
pio_gpio_init(pio, pin_miso);
pio_gpio_init(pio, pin_sck);
Expand All @@ -65,7 +65,7 @@ static inline void pio_spi_init(PIO pio, uint sm, uint prog_offs, uint n_bits,
// and this is a cheesy way to get CPOL=1
gpio_set_outover(pin_sck, cpol ? GPIO_OVERRIDE_INVERT : GPIO_OVERRIDE_NORMAL);
// SPI is synchronous, so bypass input synchroniser to reduce input delay.
hw_set_bits(&pio->input_sync_bypass, 1u << pin_miso);
hw_set_bits(&pio->input_sync_bypass, (pin_miso >= 32) ? (1u << (pin_miso - 16)) : (1u << pin_miso));

pio_sm_init(pio, sm, prog_offs, &c);
pio_sm_set_enabled(pio, sm, true);
Expand Down Expand Up @@ -150,14 +150,14 @@ static inline void pio_spi_cs_init(PIO pio, uint sm, uint prog_offs, uint n_bits
sm_config_set_in_shift(&c, false, true, n_bits);
sm_config_set_clkdiv(&c, clkdiv);

pio_sm_set_pins_with_mask(pio, sm, (2u << pin_sck), (3u << pin_sck) | (1u << pin_mosi));
pio_sm_set_pindirs_with_mask(pio, sm, (3u << pin_sck) | (1u << pin_mosi), (3u << pin_sck) | (1u << pin_mosi) | (1u << pin_miso));
pio_sm_set_pins_with_mask64(pio, sm, (2ull << pin_sck), (3ull << pin_sck) | (1ull << pin_mosi));
pio_sm_set_pindirs_with_mask64(pio, sm, (3ull << pin_sck) | (1ull << pin_mosi), (3ull << pin_sck) | (1ull << pin_mosi) | (1ull << pin_miso));
pio_gpio_init(pio, pin_mosi);
pio_gpio_init(pio, pin_miso);
pio_gpio_init(pio, pin_sck);
pio_gpio_init(pio, pin_sck + 1);
gpio_set_outover(pin_sck, cpol ? GPIO_OVERRIDE_INVERT : GPIO_OVERRIDE_NORMAL);
hw_set_bits(&pio->input_sync_bypass, 1u << pin_miso);
hw_set_bits(&pio->input_sync_bypass, (pin_miso >= 32) ? (1u << (pin_miso - 16)) : (1u << pin_miso));

uint entry_point = prog_offs + (cpha ? spi_cpha1_cs_offset_entry_point : spi_cpha0_cs_offset_entry_point);
pio_sm_init(pio, sm, entry_point, &c);
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19 changes: 10 additions & 9 deletions pio/spi/spi_loopback.c
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Expand Up @@ -49,19 +49,20 @@ void test(const pio_spi_inst_t *spi) {
int main() {
stdio_init_all();

pio_spi_inst_t spi = {
.pio = pio0,
.sm = 0
};
pio_spi_inst_t spi[2];
float clkdiv = 31.25f; // 1 MHz @ 125 clk_sys
uint cpha0_prog_offs = pio_add_program(spi.pio, &spi_cpha0_program);
uint cpha1_prog_offs = pio_add_program(spi.pio, &spi_cpha1_program);

// pio_claim_free_sm_and_add_program_for_gpio_range finds a free pio and state machine for a program and sets the gpio base correctly
const uint pin_base = MIN(PIN_SCK, MIN(PIN_MOSI, PIN_MISO));
const uint pin_count = MAX(PIN_SCK, MAX(PIN_MOSI, PIN_MISO)) - pin_base + 1;
hard_assert(pio_claim_free_sm_and_add_program_for_gpio_range(&spi_cpha0_program, &spi[0].pio, &spi[0].sm, &spi[0].offset, pin_base, pin_count, true));
hard_assert(pio_claim_free_sm_and_add_program_for_gpio_range(&spi_cpha1_program, &spi[1].pio, &spi[1].sm, &spi[1].offset, pin_base, pin_count, true));

for (int cpha = 0; cpha <= 1; ++cpha) {
for (int cpol = 0; cpol <= 1; ++cpol) {
printf("CPHA = %d, CPOL = %d\n", cpha, cpol);
pio_spi_init(spi.pio, spi.sm,
cpha ? cpha1_prog_offs : cpha0_prog_offs,
pio_spi_init(spi[cpha].pio, spi[cpha].sm,
spi[cpha].offset,
8, // 8 bits per SPI frame
clkdiv,
cpha,
Expand All @@ -70,7 +71,7 @@ int main() {
PIN_MOSI,
PIN_MISO
);
test(&spi);
test(&spi[cpha]);
sleep_ms(10);
}
}
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