Questions about conditional definitions

zhuzd

Questions about conditional definitions [Copy link]

#ifndef CONF_SERCOM_0_USART_BAUD //#define CONF_SERCOM_0_USART_BAUD 9600 #if (*(__IO uint8_t*)(((uint32_t)0x44000000))==0x01) #define CONF_SERCOM_0_USART_BAUD 2400 #elif (*(__IO uint8_t*)(SEEPROM_ADDR+15)==0x02 #define CONF_SERCOM_0_USART_BAUD 4800 #elif (*(__IO uint8_t*)(SEEPROM_ADDR+15)==0x03 #define CONF_SERCOM_0_USART_BAUD 9600 #elif (*(__IO uint8_t*)(SEEPROM_ADDR+15)==0x04 #define CONF_SERCOM_0_USART_BAUD 115200 #else #define CONF_SERCOM_0_USART_BAUD 2400 #endif #endif Why does this definition method report an error? "operator '*' has no left operand" This is the error message

zhuzd

This method was used for STM32 before. Now that we have changed to atmel studio compiler and ATSAM chip, will this method no longer work?

lcofjp

The code above is missing a lot of right brackets, but I think this is not the point. The function you want to achieve cannot be achieved by macro definition. Macro definition is processed during the preprocessing period of compilation, and the code you wrote above needs to be judged during the runtime. During the compilation period, the compiler analyzes the program on the PC. How can it know the content in the hardware circuit memory?

zhuzd

lcofjp posted on 2018-10-23 09:12 The code above lacks a lot of right brackets, but I don't think this is the point. The function you want to implement cannot be implemented by macro definition. Macro definition is in the compilation...

Oh, I know, thank you, but I remember that I used to operate stm32 like this

辛昕

lcofjp posted on 2018-10-23 09:12 The code above is missing a lot of right brackets, but I think this is not the point. The function you want to achieve cannot be achieved by macro definition. Macro definition is in the compilation...

It is really too evil. This is also a long-standing experience. What kind of evil is it that would think of determining the baud rate during compilation?