Add notes and setup file for ESP8266.

README.md

@@ -53,6 +53,7 @@ wiring details, pin names and hardware issues.
   3.7 [Class Textbox](./README.md#37-class-textbox) Scrolling text display.  
  4. [Device drivers](./README.md#4-device-drivers) Device driver compatibility
  requirements (these are minimal).  
+ 5. [ESP8266](./README.md#5-esp8266) This can work.  
 
 # 1. Introduction
 
@@ -179,6 +180,8 @@ MicroPython target and the electrical connections between display and target.
  * `esp32_setup.py` As written supports an ESP32 connected to a 128x128 SSD1351
  display. After editing to match the display and wiring, it should be copied to
  the target as `/pyboard/color_setup.py`.
+ * `esp8266_setup.py` Similar for [ESP8266](./README.md#5-esp8266). Usage is
+ somewhat experimental.
 
 The `gui/core` directory contains the GUI core and its principal dependencies:
 
@@ -797,3 +800,51 @@ Drivers for displays using I2C may need to use
 depending on the chip requirements.
 
 ###### [Contents](./README.md#contents)
+
+# 5. ESP8266
+
+Some personal observations on successful use with an ESP8266.
+
+I chose an [Adafruit 128x128 OLED display](https://www.adafruit.com/product/1431)
+to represent the biggest display I thought the ESP8266 might support. I
+reasoned that, if this can be made to work, smaller or monochrome displays
+would be no problem. 
+
+The ESP8266 is a minimal platform with typically 36.6KiB of free RAM. The
+framebuffer for a 128*128 OLED requires 16KiB of contiguous RAM (the display
+hardware uses 16 bit color but my driver uses an 8 bit buffer to conserve RAM).
+
+A further issue is that, by default, ESP8266 firmware does not support complex
+numbers. This rules out the plot module and the `Dial` widget. It is possible
+to turn on complex support in the build, but I haven't tried this.
+
+I set out to run the `scale.py` and `textbox.py` demos as these use `uasyncio`
+to create dynamic content, and the widgets themselves are relatively complex.
+
+I froze a subset of the `drivers` and the `gui` directories. A subset minimises
+the size of the firmware build and eliminates modules which won't compile due
+to the complex number issue. The directory structure in my frozen modules
+directory matched that of the source: the directory had `gui` and `drivers`
+subdirectories with their subdirectories intact (where they had necessary
+contents).
+
+In the following description, `__init__.py` was always left in place.  
+From `drivers` I removed everything except `ssd1351/ssd1351_generic.py`.  
+From `gui/fonts` I removed fonts except for `arial10`.  
+From `gui/demos` I removed all but `scale.py` and `tbox.py`.  
+From `gui/core` I removed all but `colors.py`,`writer.py` and `nanogui.py`.  
+
+I deleted unused directories such as `drivers/sharp` etc.
+
+I erased flash, built and installed the new firmware. Finally I copied
+`esp8266_setup.py` to `/pyboard/color_setup.py`. This could have been frozen
+but I wanted to be able to change pins if required.
+
+Both demos worked perfectly.
+
+I modified the demos to regularly report free RAM. `scale.py` reported 10480
+bytes, `tbox.py` reported 10512 bytes, sometimes more, as the demo progressed.
+In conclusion I think that applications of moderate complexity should be
+feasible.
+
+###### [Contents](./README.md#contents)

drivers/ssd1351/README.md

@@ -2,7 +2,7 @@
 
 There are three versions.
  * `ssd1351.py` This is optimised for STM (e.g. Pyboard) platforms.
- * `ssd1351_generic.py` Cross-platform version.
+ * `ssd1351_generic.py` Cross-platform version. Tested on ESP32 and ESP8266.
  * `ssd1351_16bit.py` Cross-platform. Uses 16 bit RGB565 color.
 
 To conserve RAM the first two use 8 bit (rrrgggbb) color. This works well with

esp8266_setup.py

@@ -0,0 +1,34 @@
+# esp8266_setup.py Copy to target as color_setup.py
+
+# Released under the MIT License (MIT). See LICENSE.
+# Copyright (c) 2020 Peter Hinch
+
+# As written, supports:
+# Adafruit 1.5" 128*128 OLED display: https://www.adafruit.com/product/1431
+# Adafruit 1.27" 128*96 display https://www.adafruit.com/product/1673
+# Edit the driver import for other displays.
+
+# WIRING (Adafruit pin nos and names).
+# Pyb   SSD
+# 3v3   Vin (10)
+# Gnd   Gnd (11)
+# IO0   DC (3 DC)
+# IO16  CS (5 OC OLEDCS)
+# IO2   Rst (4 R RESET)
+# IO14  CLK (2 CL SCK)  Hardware SPI1
+# IO13  DATA (1 SI MOSI)
+
+from machine import SPI, Pin
+import gc
+from drivers.ssd1351.ssd1351_generic import SSD1351 as SSD
+
+height = 128   # Ensure height is correct (96/128)
+
+pdc = Pin(0, Pin.OUT, value=0)  # Arbitrary pins
+pcs = Pin(16, Pin.OUT, value=1)
+prst = Pin(2, Pin.OUT, value=1)
+# Hardware SPI on native pins for performance
+spi = SPI(1, baudrate=10_000_000, polarity=0, phase=0)
+
+gc.collect()
+ssd = SSD(spi, pcs, pdc, prst, height=height)