From 834e5da770c7418c95dfe2d7e285ac18edbf2ae1 Mon Sep 17 00:00:00 2001 From: Peter Hinch Date: Mon, 25 Jan 2021 08:52:03 +0000 Subject: [PATCH] Doc changes. --- DRIVERS.md | 2 +- README.md | 26 +++++++++++++++++++++++--- 2 files changed, 24 insertions(+), 4 deletions(-) diff --git a/DRIVERS.md b/DRIVERS.md index 01b829b..492c838 100644 --- a/DRIVERS.md +++ b/DRIVERS.md @@ -44,7 +44,7 @@ a bare minimum of functionality required to support the above.      7.2.2 [EPD public methods](./DRIVERS.md#722-epd-public-methods)      7.2.3 [EPD public bound variables](./DRIVERS.md#723-epd-public-bound-variables) 8. [EPD Asynchronous support](./DRIVERS.md#8-epd-asynchronous-support) - 9. [Writing device drivers](./DRIVERS.md#8-writing-device-drivers) + 9. [Writing device drivers](./DRIVERS.md#9-writing-device-drivers) ###### [Main README](./README.md#1-introduction) diff --git a/README.md b/README.md index fd64f86..68cf415 100644 --- a/README.md +++ b/README.md @@ -56,6 +56,7 @@ wiring details, pin names and hardware issues. 3. [The nanogui module](./README.md#3-the-nanogui-module) 3.1 [Application Initialisation](./README.md#31-application-initialisation) Initial setup and refresh method.      3.1.1 [User defined colors](./README.md#311-user-defined-colors) +      3.1.2 [Monochrome displays](./README.md#312-monochrome-displays) A slight "gotcha" with ePaper. 3.2 [Label class](./README.md#32-label-class) Dynamic text at any screen location. 3.3 [Meter class](./README.md#33-meter-class) A vertical panel meter. 3.4 [LED class](./README.md#34-led-class) Virtual LED of any color. @@ -349,10 +350,12 @@ that pixels up to the edges of the display can be accessed. from color_setup import ssd # Create a display instance from gui.core.nanogui import refresh refresh(ssd, True) # Initialise and clear display. +# Uncomment for ePaper displays +# ssd.wait_until_ready() ssd.fill(0) ssd.line(0, 0, ssd.width - 1, ssd.height - 1, ssd.rgb(0, 255, 0)) # Green diagonal corner-to-corner ssd.rect(0, 0, 15, 15, ssd.rgb(255, 0, 0)) # Red square at top left -ssd.rect(ssd.width -15, ssd.height -15, 15, 15, ssd.rgb(0, 0, 255)) # Blue square at bottm right +ssd.rect(ssd.width -15, ssd.height -15, 15, 15, ssd.rgb(0, 0, 255)) # Blue square at bottom right ssd.show() ``` @@ -439,12 +442,29 @@ between 4-bit and other drivers, use `create_color()` for all custom colors: it will produce appropriate behaviour. See the `vari_fields` function in the demo `color15.py` for an example. +### 3.1.2 Monochrome displays + +Most widgets work on monochrome displays if color settings are left at default +values. If a color is specified, drivers in this repo will convert it to black +or white depending on its level of saturation. A low level will produce the +background color, a high level the foreground. This can produce a surprise on +ePaper units where the foreground is white. + +At the bit level `1` represents the foreground. This is white on an emitting +display such as an OLED. On a Sharp display it indicates reflection. On an +ePaper display it represents black. Given that `1` is the foreground color, +explicitly specifying `BLACK` on an ePaper will produce `0` as black has (very) +low saturation. In this context the resultant physically white background +color may come as a surprise. + +In general the solution is to leave color settings at default. + ###### [Contents](./README.md#contents) ## 3.2 Label class -This supports applications where text is to be rendered at specific screen -locations. +The purpose of a `Label` instance is to display text at a specific screen +location. Text can be static or dynamic. In the case of dynamic text the background is cleared to ensure that short strings cleanly replace longer ones.