Arduino for STM32

I am using Arduino IDE to program the STM32F103C8T6. It works. But I can not change the Rx and Tx Buffer size for Seiral1. I know the HardwareSerial.h have the following #defines as:
// NOTE: a "power of 2" buffer size is recommended to dramatically
// optimize all the modulo operations for ring buffers.
#if !defined(SERIAL_TX_BUFFER_SIZE)
#define SERIAL_TX_BUFFER_SIZE 64
#endif
#if !defined(SERIAL_RX_BUFFER_SIZE)
#define SERIAL_RX_BUFFER_SIZE 64
#endif
#if (SERIAL_TX_BUFFER_SIZE>256)
typedef uint16_t tx_buffer_index_t;
#else
typedef uint8_t tx_buffer_index_t;
#endif
#if (SERIAL_RX_BUFFER_SIZE>256)
typedef uint16_t rx_buffer_index_t;
#else
typedef uint8_t rx_buffer_index_t;
#endif
In the program, I using #define to define the Rx_Buffer and Tx_buffer as 256. But when I send the string longs than 64, the content exceed 64 lost.

I am appreciated if somebody could give me advise.

Best regards

Xiaofeng Cai

If you change in the sketch it is not in the scope of the Serial header to redefine it. Sketch is a cpp file.
Use the build_opt.h way as described here:
https://github.com/stm32duino/Arduino_C ... le-content

Dear fpiSTM

I read the information you mentioned, I use the Arduino IDE to program the MCU. When I put the file build_opt.h under the project sketch, the compile give the error, say no build_opt.h file. I use a AI assistant and save the file at the 'stm32duno'\libraries\STMCore. It works. But the running result is not OK. I send data to Serial1, data less the 64 appeared, exceeded data lost. I am not sure where I made mistake. But anyway, thank you for your help.

Best Regards

Cai Xiaofeng