Ich versuche auf einem STM32L476RG ein EEPROM via I2C anzusprechen. Leider scheitere ich aber offenbar bereits an der grundsätzlichen Konfig. der I2C-Schnittstelle:
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void config_i2c(void) {
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//Initialize PB13 and PB14 as SCL and SDA respectively:
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{
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RCC->AHB2ENR |= RCC_AHB2ENR_GPIOBEN;
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//Configure PB13 as SCL:
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{
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GPIOB->AFR[1] &= ~(GPIO_AFRH_AFRH5);
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GPIOB->AFR[1] |= ((uint32_t)GPIO_AF4_I2C2) << GPIO_AFRH_AFSEL13_Pos;
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GPIOB->MODER |= GPIO_MODER_MODER13_1;
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GPIOB->OTYPER |= GPIO_OTYPER_OT13;
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GPIOB->OSPEEDR |= GPIO_OSPEEDER_OSPEEDR13;
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}
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//Configure PB14 as SDA:
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{
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GPIOB->AFR[1] &= ~(GPIO_AFRH_AFRH6);
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GPIOB->AFR[1] |= ((uint32_t)GPIO_AF4_I2C2) << GPIO_AFRH_AFSEL14_Pos;
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GPIOB->MODER |= GPIO_MODER_MODER14_1;
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GPIOB->OTYPER |= GPIO_OTYPER_OT14;
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GPIOB->OSPEEDR |= GPIO_OSPEEDER_OSPEEDR14;
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}
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}
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//Initialize the I2C interface for master mode:
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{
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//Make sure HSI16 clock is turned on.
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RCC->CR |= RCC_CR_HSION;
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while(!(RCC->CR & RCC_CR_HSIRDY));
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//Select HSI16 clock as I2C2 clock.
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RCC->CCIPR |= RCC_CCIPR_I2C2SEL_1;
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//Enable the clock for the I2C interface.
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RCC->APB1ENR1 |= RCC_APB1ENR1_I2C2EN;
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//Disable the I2C peripheral.
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I2C2->CR1 &= ~(I2C_CR1_PE);
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//Configure timing for "Fast-mode".
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//(See Table 236 of the Reference Manual "RM0351, Rev 9" for the values.)
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I2C2->TIMINGR =
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(0x1u << I2C_TIMINGR_PRESC_Pos) +
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(0x9u << I2C_TIMINGR_SCLL_Pos) +
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(0x3u << I2C_TIMINGR_SCLH_Pos) +
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(0x2u << I2C_TIMINGR_SDADEL_Pos) +
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(0x3u << I2C_TIMINGR_SCLDEL_Pos);
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//"Stop" and "Restart" will be generated by software.
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I2C2->CR2 &= ~(I2C_CR2_AUTOEND);
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//Configure 7-bit addressing and set slave address.
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I2C2->CR2 &= ~(I2C_CR2_ADD10);
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I2C2->CR2 &= ~(I2C_CR2_SADD);
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I2C2->CR2 |= (NV_RAM_DEVICE_ADDRESS << 1)&0xFEul;
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//Enable the I2C peripheral.
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I2C2->CR1 |= I2C_CR1_PE;
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}
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}
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Wenn ich dann versuche, erst einmal einfach eine "Start Condition" zu generieren, passiert genau gar nichts. Das heisst, ich sehe auf dem Oszi. rein gar nichts auf den zwei Leitungen.
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void do_some_magic(void) {
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//Set transfer dir. "write".
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I2C2->CR2 &= ~(I2C_CR2_RD_WRN);
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//Configure number of bytes to be written.
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I2C2->CR2 |= 1 << I2C_CR2_NBYTES_Pos;
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//Generate "Start Condition".
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I2C2->CR2 |= I2C_CR2_START;
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while(I2C2->CR2&I2C_CR2_START); //<-- HIER DREHT ES "FOREVER"
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return;
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}
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Was muss ich noch "enablen", "clearen" etc. oder was sonst ist falsch?
