timeular/notes.org

MicroPython Implementation Notes

• Backup Up firmware, flashing, etc.
  • Backup existing firmware from 4M Flash ESP32
  • Update Flash from backup
  • Erase Flash
  • Flash with MicroPython
• Circuit Layout
• SSD 1306
• MPU 6050
• Turn off MPU (through vext, also turns off screen)
• Wifi Connection Example, outbound requests.
• Getting a Unique ID for this instance
• NTP
• Web Server
• Connections
• [3/8] Things to look at

Backup Up firmware, flashing, etc.

On lolin32, need to hold down the reset while esptool is connecting, and then release to get this to work.

Backup existing firmware from 4M Flash ESP32

esptool.py -b 115200 --port /dev/ttyUSB0 read_flash 0x00000 0x400000 lolin32_original.bin

Update Flash from backup

esptool.py -b 115200 --port /dev/ttyUSB0 write_flash --flash_freq 80m 0x000000 lolin32_original.bin

Erase Flash

esptool.py -b115200  --port /dev/ttyUSB0 erase_flash

Flash with MicroPython

esptool.py --chip esp32 --port /dev/ttyUSB0 write_flash -z 0x1000 ~/Downloads/esp32-idf3-20200902-v1.13.bin

Circuit Layout

Pin	Used For
37	SDA - MPU6050
36	SCL - MPU6050

SSD 1306

from machine import I2C, Pin
import ssd1306

rst = Pin(16, Pin.OUT)
rst.value(1)
scl = Pin(15, Pin.OUT, Pin.PULL_UP)
sda = Pin(4, Pin.OUT, Pin.PULL_UP)
i2c = I2C(scl=scl, sda=sda, freq=450000)
oled = ssd1306.SSD1306_I2C(128, 64, i2c, addr=0x3c)

oled.fill(0)
oled.text('ESP32', 45, 5)
oled.text('MicroPython', 20, 20)
oled.show()

MPU 6050

from machine import I2C, Pin
from mpu6050 import accel

scl=Pin(36, Pin.OUT)
sda=Pin(37, Pin.OUT)
i2c = I2C(scl=scl, sda=sda, freq=450000)
a = accel(i2c)
a.get_values()

Turn off MPU (through vext, also turns off screen)

from machine import Pin

vext = Pin(21, Pin.OUT, Pin.PULL_HOLD)
vext.value(0) # Turns ON Vext
vext.value(1) # Turns OFF Vext
machine.deepsleep()

Wifi Connection Example, outbound requests.

import network
import machine
wlan = network.WLAN(network.STA_IF)
wlan.active(True)
binary_id = machine.unique_id()
hostname = 'timeular-{:02x}{:02x}{:02x}{:02x}'.format(binary_id[0],binary_id[1], binary_id[2], binary_id[3])
wlan.config(dhcp_hostname='timeular')
wlan.connect("Hart's",'D187wn644GeH')
wlan.if_config()

Getting a Unique ID for this instance

import machine
binary_id=machine.unique_id()
hex_id = '{:02x}{:02x}{:02x}{:02x}'.format(binary_id[0],binary_id[1],binary_id[2],binary_id[3])

This can be used to append to e.g. the DHCP hostname to make it likely to be unique.

NTP

import ntptime
ntptime.settime()
import machine
rtc = machine.RTC()
rtc.datetime()

Web Server

import picoweb
from network import WLAN, STA_IF

app = picoweb.WebApp('main')

@app.route("/")
def index(req,resp):
    yield from picoweb.start_response(resp)
    yield from resp.awrite("Hello world from picoweb running on the ESP32")
 
app.run(debug=True,host=WLAN(STA_IF).ifconfig()[0],port=80)

Connections

Pin 23 ESP -> SDA MPU Pin 19 ESP -> SCL MPU

MPU AD0 -> - Rail MPU GND -> - Rail MPU Vcc -> + RailArduino MPU 6050 Serial Monitor

ESP GND -> - Rail ESP VEXT -> +Rail

[3/8] Things to look at

• Can we turn off the MPU with VEXT Control? (ESP Pin 21).
• Connecting to WiFi - Client Mode
• Connecting to WiFi - Direct Mode
• BLE?
• NTP?
• How to store the data appropriately - Flash/SqlLite, RTC memory?
• How to retrieve data over WiFi
• How to detect battery low
• WiFiManager