touch_cal Directory Reference

Directory dependency graph for touch_cal:

Directories
	src

Detailed Description

Interactive N-point affine touch calibration (#262), wiring the weighted least-squares solver in libs/ra8_touch_cal end to end over the real GoodIX GT911 driver (ra8_touch on IIC_B) and the real GLCDC display path (ra8_display_pal on ra8_glcdc): present targets, collect raw samples, solve the transform, apply it and verify.

For each of five targets – four inset corners and the panel centre – it paints a white cross-hair and blocks on one settled raw GT911 sample. tc_draw_target and tc_read_raw are the two dependency-inversion seams ra8_touch_cal is written against, and they also record the target/raw pair so the verify pass can measure the residual. On a successful solve it serialises the matrix, loads it back, re-applies it to every captured raw and paints a green corrected cross-hair at each mapped pixel – a live cross-hair landing on its target is the visible proof. The largest residual is the fit error.

The panel framebuffer is 512x512, not 1024x600. The full panel buffer does not fit in on-chip SRAM, so the app scans a 512x512 RGB565 framebuffer, the same size glcdc_render uses. That is a hardware constraint, not a simplification.

The bring-up sentinel is finger-free on purpose

The solve is only reachable once five distinct raw samples arrive, which on silicon means a human tapping five cross-hairs. So the deterministic part of the verdict is a separate ready line that prints once the panel and touch driver are up, whether or not any tap arrived; a solver regression still trips the gate through the explicit failure verdicts. With no finger the app reports a skipped calibration and the ready line still holds, so the same gate is meaningful on a staffed bench and on an unattended one.

On the bench the GT911 lives on the ereader carrier's I2C0 bus and the TFT on the parallel RGB interface. Tap each cross-hair as it appears; the app solves the transform, stores it ready for ra8_flash page storage, and paints the corrected cross-hairs so you can see the correction land.