Category: Science

This guide will help set up a Mac OS computer to program an ATtiny 85 using the USB Tiny AVR Programmer from Sparkfun and the Arduino IDE.

Required Items:

• Sparkfun Tiny AVR Programmer (Sparkfun) – This is a handy USB based programmer for ATtiny microcontrollers. It is powered by an ATtiny84 that is set up as a USBtinyISP programmer. The board has an 8 pin socket to hold a ATtiny45/85 microcontroller that you want to program.
• ATtiny 85 Microcontroller (Digikey) – The ATtiny85 is a low-power 8-bit microcontroller based on the AVR enhanced RISC architecture.
• Arduino IDE (Download)
• Mac computer (e.g. MacBook Pro) with OS 10.14 or later

I used the following steps to get the Sparkfun Tiny AVR Programmer working on my Mac. Hopefully this will be helpful for you as well. Your experience may vary.

Step 1: Install ATtiny85

Install the ATtiny 85 into the programmer. Make sure you orient the chip so that pin 1 (usually identified by a dot) is by the notch. Once this is installed, plug the USB into your computer. You will not see a light and Mac OS will not recognize it as a serial port (don’t worry).

Step 2: Set up Arduino IDE

Install the Arduino IDE software (Download) and navigate the menu Arduino -> Preferences and in the field for “Additional Board Manager URL” paste this link:

https://raw.githubusercontent.com/damellis/attiny/ide-1.6.x-boards-manager/package_damellis_attiny_index.json

Click “OK” to save and restart the Arduino IDE. Navigate the menu Tools -> Board -> Boards Manger and type “attiny” into the top search board and there will click on the “Install” button on the attiny board package.

You should now see an entry for ATtiny in the Tools > Board menu. Select “ATtiny25/45/85”.

For “Processor” select the chip you are using, e.g. ATiny85.

For “Programmer” select “USBtinyISP“

For “Clock” unless you have an external crystal in your circuit, you should select “Internal” and 1 MHz seems to be fine for most projects.

Finish by clicking “Burn Bootloader“. You should see the LED on the programmer flash. If it doesn’t work, you may need to Quit the Arduino IDE and restart to try again.

Please note: On the Mac, you do NOT select a serial “Port”. The IDE will program the ATtiny through the USBtinyISP that is loaded on the Tiny AVR Programmer board.

Step 3: Program your ATtiny85

You can use the example blink test to make sure you can program your ATtiny85. You can use the built in blink test but you will need to change the LED_BUILTIN to be 0 (zero). You can also copy and past the following code:

void setup() {
  pinMode(0, OUTPUT);
}
void loop() {
  digitalWrite(0, HIGH);   
  delay(1000);                       
  digitalWrite(0, LOW); 
  delay(1000); 
}

Arduino 1.x IDE: Click the upload button (right arrow) or press Command-U.

Arduino 2.x IDE: Select Sketch > Upload Using Programmer or Shift-Command-U

Once uploaded, the built-in LED should start to flash.

The ATtiny85 has PWM (Pulse Width Modulation) outputs so you can use the analogWrite() function to adjust the brightness of the LED from 0 to 255. Here is an example that fades the LED.

/*
  Fade
  This example shows how to fade an LED on using the analogWrite()
  function.
  The analogWrite() function uses PWM, so if you want to change the pin you're
  using, be sure to use another PWM capable pin. On most Arduino, the PWM pins
  are identified with a "~" sign, like ~3, ~5, ~6, ~9, ~10 and ~11.
*/
int led = 0;           // the PWM pin the LED is attached to
int brightness = 0;    // how bright the LED is
int fadeAmount = 1;    // how many points to fade the LED by
void setup() {
  pinMode(led, OUTPUT);
}
void loop() {
  analogWrite(led, brightness);
  brightness = brightness + fadeAmount;
  // reverse the direction of the fading at the ends of the fade:
  if (brightness <= 0) {
     analogWrite(led, 0);   
     delay(1500);
     fadeAmount = -fadeAmount;
  }
  if(brightness >= 255) {
    fadeAmount = -fadeAmount;
  }
  delay(10);
}

References

This was tested on Arduino 1.x and 2.x IDEs, on an Intel i7 based Apple MacBook Pro and on an M2 based MacBook Air using an USB-C to A adapter.

• High-low tech: Programming an ATtiny w/ Arduino 1.6 (or 1.0) – http://highlowtech.org/?p=1695
• Instructables: Program an ATtiny With Arduino – https://www.instructables.com/id/Program-an-ATtiny-with-Arduino/
• Getting started with Atmel ATtiny85 (AVR Programming) – https://electronut.in/getting-started-with-attiny85-avr-programming/
• Programming with AVRdude – https://learn.adafruit.com/introducing-trinket/programming-with-avrdude
• Crosspack for AVR Development – https://www.obdev.at/products/crosspack/index.html
• How to Program an Attiny85 From an Arduino Uno – https://www.instructables.com/id/How-to-Program-an-Attiny85-From-an-Arduino-Uno/
• Programming the ‘AtTiny85’ With the ‘Tiny AVR Programmer’ and Supplemented ‘Arduino IDE’ – https://www.instructables.com/id/Programming-an-Atmel-AtTiny85-using-Arduino-IDE-an/

I’ve always wanted to add a backyard weather station to help record not just temperature data, but humidity, pressure, rainfall, wind speed and UV levels. My recent experiments introduced me to the ESP8266 NodeMCU, a low-cost microcontroller with embedded WiFi. I just needed to add a solar cell, a battery, a sensor and an enclosure.

Solar Power

I found a 2.5W 5V/500mAh solar cell (from Amazon) and a 3.7V 3000mAh rechargeable Li-ion battery pack (Amazon). After some research (see here), I added a TP4056 charger module (Amazon) that regulates the charging and protects the battery from overcharge.

I added a 0.1uF ceramic capacitor and 100uF electrolytic capacitor to smooth the output voltage. I used a simple 3.3v voltage regulator (DigiKey) to feed the 3.3v bus for the ESP8266 and sensors.

Monitoring the voltage coming from the solar cell and/or battery would help determine if the system is getting enough power during the day to keep the system running at night. The ESP8266 has an analog input (A0) that can be used to determine the output voltage but it can only handle up to 3.3v. By using a simple 2 resistor divider circuit (see right) I could monitor the voltage and apply a multiplier to get to the actual voltage I measured with a multimeter. In this case, the A0 pin was reporting 907 when the multimeter was showing 4.69v so I used 4.69 / 907.0 and further sampled other readings to ensure I had the correct value.

Circuit Design

The sensors I wanted to add included a BME280 pressure and humidity sensor, a one-wire DS18B20 temperature sensor and a 2N2222 transistor powered rain detector. I put the circuit together using a simple breadboard and started on the code.

Using the free open source KiCad electronic design software, I build a schematic drawing to help build the final non-breadboarded product.

Getting Started with Arduino IDE and ESP8266

The ESP8266 NodeMCU has a USB port that allows the microcontroller to be easily powered and programmed with the Arduino IDE . However, it is not as easy to set up and use as an Arduino device. I found out that you will need to install a driver to see the device on my MacBook (see here for MacOS instructions and download the USB to UART Bridge VCP Drivers here). Once the driver is installed, the Arduino IDE needs to be set up to manage the NodeMCU. The ESP8266 I purchased came with some instructions:

Instruction & Steps of How to use:
1. Download and Install the Arduino IDE (download here)
2. Set up your Arduino IDE as: Go to File->Preferences and copy the URL below to get the ESP board manager extensions: http://arduino.esp8266.com/stable/package_esp8266com_index.json
3. Go to Tools > Board > Board Manager> Type “esp8266” and download the Community esp8266 and install.
4. Set up your chip as:
Tools -> Board -> NodeMCU 1.0 (ESP-12E Module)
Tools -> Flash Size -> 4M (3M SPIFFS)
Tools -> CPU Frequency -> 80 Mhz
Tools -> Upload Speed -> 921600
Tools -> Port -> (whatever it is)
5. In Arduino IDE, look for the old fashioned Blink program. Load, compile and upload. Go to FILE> EXAMPLES> ESP8266> BLINK

Code

Once I had the ESP8266 connected, I could start creating the code. The code is available here: https://github.com/jasonacox/WeatherStationWiFi

Rain Sensor

Using a simple NPN transistor, you can detect the presence of water. I wanted to detect rain which mean that I needed to add a couple of electrodes connected to that transistor (for detection) and our power supply. Water allows a small amount of current to pass through it to detect water, you will need to amplify it, hence the need for the transistor which turns a low current into a switch to a much larger current. The ESP8266 digital inputs can see the switched power from the transistor and can indicate water has been detected.

Wind Speed Sensor with an Anemometer

An anemometer is a device used to catch the wind and record its speed.

I found a 3D model on https://www.thingiverse.com/thing:2559929

More to come…

Installation