Esp01 Datasheet |best| -

– Functional but dangerously incomplete.

| GPIO0 | GPIO2 | GPIO15 (not on ESP-01!) | Mode | |-------|-------|------------------------|------| | 1 | 1 | 0 | Boot from Flash (Normal run) | | 0 | 1 | 0 | UART Download (Firmware upload) | | Missing: SDIO boot modes, effect of GPIO15 (not exposed on ESP-01, but tied to GND internally) esp01 datasheet