Use copy_to_ram to (hopefully) improve stability #5
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By keeping the BT firmware in flash, There's just enough RAM to copy the entire code to RAM.
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This PR aims to improve audio streaming stability by using
copy_to_ramto run the entire program from RAM.By default, the Pico runs code directly from flash over QSPI by using eXecute in Place (XIP), with a 16KB cache. This works fine for many applications which are small, or not too timing sensitive. Unfortunately, Pico-ASHA is not small, and it is latency sensitive.
However, I saw that so long as I can keep the Wifi/BT firmware in flash, there is just enough RAM for the program, variables and buffers. Therefore, I have used the
copy_to_ramfunctionality of the Pico SDK to copy all code to RAM on startup, and execute from RAM.To make the code smaller, cmake should be configured to use the
MinSizeRelconfiguration (this builds with-Osinstead of-O3).Anecdotally, with this change, I have noticed that audio streaming is much more stable. My hearing aids are still disconnecting on occasion, but far less often than before this change, and reconnection is generally more reliable. Note I am currently not performing any pre-buffer strategies to minimize latency.