In reply to @antisvin: Sorry for the late reply. I’m very busy these days. Yes, I’ve tried -Os (see Link optimization), but unfortunately the USB CDC serial becomes unavailable under -Os option. So I couldn’t communicate with DS. No patch to correct this behavior with DaisyArduino was released up to now. QSPI may solve the problem, and according to ElectroSmith, the Daisylibrary will support code storage on QSPI in the upcoming version. I’m just waiting for that.