I'm currently using an STM32F103C8 (With an arduino core) to read 4 sensors at 1kHz, then send that data via UART (at 115200 baud) to another device. Each sensor returns a float, I also include an unsigned long representing milliseconds since boot time. This adds up to be a 20 byte package, that I attempt to send at 1kHz. Sensor sampling is carried out via a timer interrupt, as it is crucial the time between samples is constant.

The data transmission itself (If I send it slowly) takes approx. 70 microseconds. When sped up to 1kHz, it takes approx. 2500. I assume this is because I am filling a serial buffer of some sort.

Is this about the limit of the communication method? If it takes longer than 1000 microseconds to send the data, then presumably the interrupt will trigger before the data is sent and it will have to start again?