diff --git a/nrf52-stepper/index.html b/nrf52-stepper/index.html
index f9df329b54dd16e9cf738b1ea1b331ed5e6e0052..0f520fe00988baa5636a594d60118bca7f4ef232 100644
--- a/nrf52-stepper/index.html
+++ b/nrf52-stepper/index.html
@@ -15,7 +15,9 @@ pre code {
 <a href='nrf52-stepper-layout.png'><img src='nrf52-stepper-layout.png' height=300px></a>
 <a href='nrf52-stepper-traces.png'><img src='nrf52-stepper-traces.png' height=300px></a>
 <a href='nrf52-stepper-interior.png'><img src='nrf52-stepper-interior.png' height=300px></a>
-<p>This is a stepper motor controller built around the DRV8825 and the nRF52.</p>
+<p>This is a stepper motor controller built around the DRV8825 and the nRF52.  The nRF52 receives commands over the radio and controls the motor, which means we only need to deliver power to the motor, no data lines.</p>
+
+<p>This board uses a PWM output and a low pass filter to deliver a voltage level to control the current limiting value for the DRV8825.  A 10K resistor and a 1uF capacitor do a reasonably good job smoothing the 10kHz PWM into a constant voltage level.</p>
 
 <p>Some sample firmware is available below (or as files: <a href='nrf52-drv8825/nrf52-drv8825.ino'>nrf52-drv8825.ino</a> and <a href='nrf52-drv8825/radio.h'>radio.h</a>).  This code defines a command set issued over the radio for moving a number of steps, changing stepping speed, setting microstepping parameters, and setting a current limit value.</p>