Posted on March 17, 2018 at 06:20 ,
,
Aha.
,
So my confusion was partly from using an old version of the ST libraries, which ,has a section of the gpio header with:
♯ define
GPIO_AF_I2C1
((
uint8_t
)
0x04
)
/* I2C1 Alternate Function mapping */
♯ define
GPIO_AF_I2C2
((
uint8_t
)
0x04
)
/* I2C2 Alternate Function mapping */
♯ define
GPIO_AF_I2C3
((
uint8_t
)
0x04
)
/* I2C3 Alternate Function mapping */
That confused me, so looking at the manual, I saw that indeed AF4 was allocated for I2C1..3. But what I missed was that AF9 is also a candidate for I2C1..3 connections.
Now that I look into the actual pin function matrix in the device datasheet per your recommendation, I do see that for PB9, AF4 = I2C1_SDA, but AF9 = I2C2_SDA , for PB9.
,
Which led me to check further in st32f4xx_gpio.h, and sure enough, it has:
♯ define
GPIO_AF9_I2C2
((
uint8_t
)
0x09
)
/* I2C2 Alternate Function mapping (Only for STM32F401xx/STM32F410xx/STM32F411xE/STM32F412xG/STM32F413_423xx Devices) */
♯ define
GPIO_AF9_I2C3
((
uint8_t
)
0x09
)
/* I2C3 Alternate Function mapping (Only for STM32F401xx/STM32F411xE/STM32F412xG and STM32F413_423xx Devices) */
So I just had to be cognizant of heterogenous ,mappings for the pin muxes, and make the right choices for my project using the old ST libraries.
,
Generating a minimum working example using CubeMX, it does correctly select the pin-specific AF value:
GPIO_InitStruct.
Alternate
=
GPIO_AF9_I2C2,
I swear, 'It was right there in the damn datasheet' is going to be the quote on my tombstone ... ,
