The stock 1500 Mbps (the P4 maximum) makes the DSI transmit each line in
a tight burst, so the framebuffer reads are bursty and lose the PSRAM
bus to the Wi-Fi SDIO DMA under load. 720 spreads the read out and
tolerates the contention. Espressif's documented underrun mitigation;
the floor at this pixel clock is ~480 Mbps.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01LKPbR6DY2JygHbyLjxm7Uu
The blue flicker during voice activity is a MIPI-DSI framebuffer-read
underrun on the PSRAM bus, not tearing. The DSI DMA reads the 800x800
framebuffer continuously (~138 MB/s at the stock 80 MHz clock); under
load the Wi-Fi (esp-hosted SDIO) and audio-playback DMA on the same
PSRAM bus starve the DSI FIFO, which the hardware then paints blue
("lcd.dsi.dpi: can't fetch data from external memory fast enough").
Drop the DPI pixel clock to 40 MHz (~54 fps): halves the continuous
read and gives the FIFO slack to ride out bursty SDIO latency spikes.
Still smooth for the face UI, and lowers display power.
Vendored as a local component because managed_components/ is gitignored
(same pattern as the esp_hosted fork) — a local component overrides the
same-named waveshare/ managed dependency, so the fix survives a clean
build.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01LKPbR6DY2JygHbyLjxm7Uu
jpmschweitzerandClaude Opus 4.8