aerosol / exodust

:smoking: PM2.5/PM10 pollution sensor built with Nerves

Exodust

PM2.5/PM10 pollution sensor built with Nerves.

Roadmap:

1. Target builds:

   • Local UART (QinHeng Electronics HL-340)
   • GPIO/UART (Raspberry Pi)
   • GPIO (NodeMCU V3/ESP8266-12)

Local UART

Prerequisites

• Kernel module: ch341
• Group membership: sudo gpasswd -a $NERVES_USER uucp

RPi

TBD

NodeMCU

TBD

SDS011

Interface specification:

Pin	Name	explain
1	CTL	Control pin, reserved
2	1um	>0.3 Micron particle concentration, PWM Output
3	5V	5V power input
4	25um	>2.5 Micron particle concentration, PWM Output
5	GND	GND
6	R	Serial port receiver RX
7	T	Serial port transmission TX

The pitch of Interface is 2.54mm

Communication protocol:

Serial communication protocol: 9600 8N1. (Rate of 9600, data bits 8, parity none, stop bits 1)

Serial report communication cycle: 1+0.5 seconds

Data frame (10 bytes):

message header + order+ data(6 bytes) + checksum + message trailer

The number of bytes	Name	Content
0	message header	AA
1	order	C0
2	data 1	PM2.5 low byte
3	data 2	PM2.5 high byte
4	data 3	PM10 low byte
5	data 4	PM10 high byte
6	data 5	0(reserved)
7	data 6	0(reserved)
8	checksum	checksum
9	message trailer	AB

Content details

Checksum: data 1 + data 2 + ...+ data 6

PM2.5 data content: PM2.5 (ug/m3) = ((PM2.5 high byte*256 ) + PM2.5 low byte)/10

PM10 data content: PM10 (ug/m3) = ((PM10 high byte*256 ) + PM10 low byte)/10

Nerves

Targets

Nerves applications produce images for hardware targets based on the MIX_TARGET environment variable. If MIX_TARGET is unset, mix builds an image that runs on the host (e.g., your laptop). This is useful for executing logic tests, running utilities, and debugging. Other targets are represented by a short name like rpi3 that maps to a Nerves system image for that platform. All of this logic is in the generated mix.exs and may be customized. For more information about targets see:

https://hexdocs.pm/nerves/targets.html#content

Getting Started

To start your Nerves app:

• export MIX_TARGET=my_target or prefix every command with MIX_TARGET=my_target. For example, MIX_TARGET=rpi3
• Install dependencies with mix deps.get
• Create firmware with mix firmware
• Burn to an SD card with mix firmware.burn

Learn more

• Official docs: https://hexdocs.pm/nerves/getting-started.html
• Official website: http://www.nerves-project.org/
• Discussion Slack elixir-lang #nerves (Invite)
• Source: https://github.com/nerves-project/nerves