e1608: a configurable generator update rate, and the achieved rate in the Analog out panel

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

README.md

@@ -123,11 +123,17 @@ click on a result fills the address, or **Use MAC** fills the MAC and leaves the
 saved: only the filled field is. A MAC with no subnet is looked up by a broadcast sent on every up interface: a
 single limited broadcast leaves through the default route only, and on 2026-11-02 it missed a real board on
 `net0` while the default route was `wlan0`. The form also groups the acquisition settings (scan rate, external clock,
-trigger, restart after an overrun, factory calibration, the digital poll rate), a range per analog input, and the
+trigger, restart after an overrun, factory calibration, the digital poll rate, the generator update rate), a range per analog input, and the
 direction and initial value of each digital line. The analog inputs are the plotted channels; each digital input
 and the counter is an extra channel only if you ask for it. Two side-stack tabs belong to it: **Analog out**
 (per DAC: a static level, or a sine, square, triangle or ramp from 0.1 to 10 Hz) and **Digital I/O** (a live LED per
 input bit, a switch per output bit, the counter with a reset); they are insensitive while no board is connected.
+The waveform generator writes the DACs at the **generator update rate** (`gen_rate`, 1 to 200 Hz, default 50), which
+is separate from the input poll rate (`poll_rate`, which only reads the digital inputs and the counter). Each update
+is a synchronous command to the board, so a board that answers slowly achieves less than was asked: the **Analog out**
+tab ends with an **Update rate** row that shows the rate the generator actually achieved (measured over about a
+second) next to the requested one, or `off` when no generator runs. The waveform frequency itself is still limited
+to 0.1 to 10 Hz.
 Acquisition is hardware-paced only (the scan rate or an external clock), the channels times the rate must stay at
 or below 250 kS/s, and the form refuses more. With the command-line options, a run that names no `aiN` key gets
 `ai0=BIP10V`; naming any `aiN` key drops that default, so `ai1=BIP5V` alone is channel 1 alone.