From c9fecc93e74da5c8f93a4d700cce96e556e072df Mon Sep 17 00:00:00 2001
From: kimonm <40135180+kimonm@users.noreply.github.com>
Date: Mon, 15 Apr 2019 12:45:37 -0700
Subject: [PATCH] Voltage range of ADC is at the chip pin (#224)
Clarify that this component uses voltage range at the chip pin, but voltage range at the board pin can be greater (e.g., for NodeMCU)
## Description:
**Related issue (if applicable):** fixes
**Pull request in [esphome](https://github.com/esphome/esphome) with YAML changes (if applicable):** esphome/esphome#
**Pull request in [esphome-core](https://github.com/esphome/esphome-core) with C++ framework changes (if applicable):** esphome/esphome-core#
## Checklist:
- [ ] Branch: `next` is for changes and new documentation that will go public with the next ESPHome release. Fixes, changes and adjustments for the current release should be created against `current`.
Co-authored-by: Otto Winter
---
components/sensor/adc.rst | 14 ++++++++++++--
1 file changed, 12 insertions(+), 2 deletions(-)
diff --git a/components/sensor/adc.rst b/components/sensor/adc.rst
index d9ec0f08c..cf5941300 100644
--- a/components/sensor/adc.rst
+++ b/components/sensor/adc.rst
@@ -38,8 +38,18 @@ Configuration variables:
.. note::
- On the ESP8266, the voltage range is 0 to 1.0V - so to measure any higher voltage you need to scale the voltage
- down using, for example, a voltage divider circuit.
+ This component prints the voltage as seen by the chip pin. On the ESP8266, this is always 0.0V to 1.0V
+ Some development boards like the Wemos D1 mini include external voltage divider circuitry to scale down
+ a 3.3V input signal to the chip-internal 1.0V. If your board has this circuitry, add a multiply filter to
+ get correct values:
+
+ .. code-block:: yaml
+
+ sensor:
+ - platform: adc
+ # ...
+ filters:
+ - multiply: 3.3
.. _adc-esp32_attenuation: