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I2C4 AF Pin Mapping Updates #701

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5f84617
added pin map containing alt. function (AF) mappings for supported I2…
stephenhensley Jun 4, 2026
3bdb835
added missing pin configurations for Seed Rev5, and PatchSM
stephenhensley Jun 10, 2026
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111 changes: 93 additions & 18 deletions src/per/i2c.cpp
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Original file line number Diff line number Diff line change
@@ -1,9 +1,96 @@
#include "per/i2c.h"
#include "sys/system.h"
#include "util/scopedirqblocker.h"
#include "daisy_core.h"

namespace daisy
{
/** pin type for pin-map arbitration */
enum class I2CPinType : uint8_t
{
SCL,
SDA
};

/** Entry for array of pin mappings */
struct I2CPinEntry
{
Pin pin;
I2CHandle::Config::Peripheral periph;
I2CPinType type;
uint8_t af;
};

/** Map containing valid GPIO and their Alternate Function values */
static constexpr I2CPinEntry kI2CPinMap[] = {
{Pin(PORTB, 6),
I2CHandle::Config::Peripheral::I2C_1,
I2CPinType::SCL,
GPIO_AF4_I2C1},
{Pin(PORTB, 6),
I2CHandle::Config::Peripheral::I2C_4,
I2CPinType::SCL,
GPIO_AF6_I2C4},
{Pin(PORTB, 7),
I2CHandle::Config::Peripheral::I2C_1,
I2CPinType::SDA,
GPIO_AF4_I2C1},
{Pin(PORTB, 7),
I2CHandle::Config::Peripheral::I2C_4,
I2CPinType::SDA,
GPIO_AF6_I2C4},
{Pin(PORTB, 8),
I2CHandle::Config::Peripheral::I2C_1,
I2CPinType::SCL,
GPIO_AF4_I2C1},
{Pin(PORTB, 8),
I2CHandle::Config::Peripheral::I2C_4,
I2CPinType::SCL,
GPIO_AF6_I2C4},
{Pin(PORTB, 9),
I2CHandle::Config::Peripheral::I2C_1,
I2CPinType::SDA,
GPIO_AF4_I2C1},
{Pin(PORTB, 9),
I2CHandle::Config::Peripheral::I2C_4,
I2CPinType::SDA,
GPIO_AF6_I2C4},
{Pin(PORTB, 10),
I2CHandle::Config::Peripheral::I2C_2,
I2CPinType::SCL,
GPIO_AF4_I2C2},
{Pin(PORTB, 11),
I2CHandle::Config::Peripheral::I2C_2,
I2CPinType::SDA,
GPIO_AF4_I2C2},
{Pin(PORTD, 12),
I2CHandle::Config::Peripheral::I2C_4,
I2CPinType::SCL,
GPIO_AF4_I2C4},
{Pin(PORTD, 13),
I2CHandle::Config::Peripheral::I2C_4,
I2CPinType::SDA,
GPIO_AF4_I2C4},
{Pin(PORTH, 4),
I2CHandle::Config::Peripheral::I2C_2,
I2CPinType::SCL,
GPIO_AF4_I2C2},
};

/** Searches the pin map for a match, and returns the alternate function for that configuration.
* If no match is found, AF4 is returned (all AF4_I2Cx in STM32HAL are the same value).
*/
constexpr uint8_t
FindAltFn(const Pin& p, I2CHandle::Config::Peripheral periph, I2CPinType type)
{
for(const auto& entry : kI2CPinMap)
{
if(entry.pin == p && entry.periph == periph && entry.type == type)
return entry.af;
}
return GPIO_AF4_I2C1;
}

/** Private implementation for I2CHandle */
class I2CHandle::Impl
{
Expand Down Expand Up @@ -614,27 +701,15 @@ void I2CHandle::Impl::InitPins()
GPIO_InitStruct.Mode = GPIO_MODE_AF_OD;
GPIO_InitStruct.Pull = GPIO_NOPULL;
GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
switch(config_.periph)
{
case I2CHandle::Config::Peripheral::I2C_1:
GPIO_InitStruct.Alternate = GPIO_AF4_I2C1;
break;
case I2CHandle::Config::Peripheral::I2C_2:
GPIO_InitStruct.Alternate = GPIO_AF4_I2C2;
break;
case I2CHandle::Config::Peripheral::I2C_3:
GPIO_InitStruct.Alternate = GPIO_AF4_I2C3;
break;
case I2CHandle::Config::Peripheral::I2C_4:
GPIO_InitStruct.Alternate = GPIO_AF6_I2C4;
break;
default: break;
}

port = GetHALPort(config_.pin_config.scl);
port = GetHALPort(config_.pin_config.scl);
GPIO_InitStruct.Alternate
= FindAltFn(config_.pin_config.scl, config_.periph, I2CPinType::SCL);
GPIO_InitStruct.Pin = GetHALPin(config_.pin_config.scl);
HAL_GPIO_Init(port, &GPIO_InitStruct);
port = GetHALPort(config_.pin_config.sda);
port = GetHALPort(config_.pin_config.sda);
GPIO_InitStruct.Alternate
= FindAltFn(config_.pin_config.sda, config_.periph, I2CPinType::SDA);
GPIO_InitStruct.Pin = GetHALPin(config_.pin_config.sda);
HAL_GPIO_Init(port, &GPIO_InitStruct);
}
Expand Down
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