first commit

labs/004_button_pullup_pulldown/firmware.md

@@ -0,0 +1,22 @@
+# Firmware
+
+## Expected Behavior
+
+- Configure GPIO as input.
+- Read button state.
+- Print state to serial or toggle LED.
+- Optional: compare external resistor with internal pull-up.
+
+## Physical Test Procedure
+
+1. Measure GPIO idle voltage.
+2. Press button and measure GPIO voltage.
+3. Run firmware and compare serial/LED state with measurements.
+
+## Code
+
+TODO: добавить firmware после выбора GPIO и workflow.
+
+## Actual Result
+
+TODO: записать фактическое поведение.