问题
I'm using RN42 (http://www.microchip.com/wwwproducts/en/RN42) bluetooth module at 115200 bauds (UART SSP mode) to send very small (1 - 20 byte) serial data messages between a computer and a ATMega328 MCU. I find that the latency for one message is somewhere around 60 - 100 ms. I would need 10 ms or less in my application. I'm wondering if this is even possible with bluetooth 2.1 devices.´
I know that theoretically bluetooth packets can be sent every 2 * 625 us from one end since 625 us is the frequency hopping interval. Also, one package will always have a minimum of 126 + payload bits. If we are sending 10 bytes (80 bits), the minimum latency based on 115200 baud rate should be (126+80)/115200*1000 + 2 * 0.625 = 3 ms. However, when I measure the latency with a test code, the minimum latency will not go below 60 ms. This suggests that the baud rate or the frequency hopping are not the dominant causes of latency and for some reason the packages are not sent at a maximum rate.
Does someone know if < 60 ms latency is technically possible with this setup and if so, how to achieve it?
来源：https://stackoverflow.com/questions/37250028/what-is-the-minimum-packet-latency-that-can-be-achieved-with-classic-bluetooth