Week 15: networking and communications

Experience: Using RF433MHZ

Objetive:

Implement and interpret networking protocols

Links:

Resources:

INO Rx code
INO Tx code
BRD Eagle board design Rx
SCH Eagle schematic Rx
BRD Eagle board design Tx
SCH Eagle schematic Tx

433MHz RF

I decided to use the 433 MHz RF module for the assignment because I am going to use it in final project. Technical details: 433MHz, 500ft range (given perfect conditions), 4800bps data rate, 5V supply voltage

2 boards with ATTINY85

I made 2 boards to use the TX and RX 433MHz RF module but also left the pins to make a connection with the L2C protocol

TX board diagram

I use an ATTINY85 microprocessor, 1 power LED, 1 led as transmission signal, resistors, capacitor, pins for programming, pins for L2C connection and pins for the 433MHz RF transmitter module

Schematic view

This is the schematic made in EAGLE and can be downloaded in the resources section

Board 1 completed

This is an image of how board 1 looks finished, accidentally spilled some tin on the right side and I could not remove it

RX board board

This is the diagram of the board 2, the only difference is that it has an additional pin because that way the RX module of the 433MHz RF

Schematic view

Iquals to the board 1, I use an ATTINY85 microprocessor, 1 power LED, 1 led as transmission signal, resistors, capacitor, pins for programming, pins for L2C connection and pins for the 433MHz RF receiver module

Board 2 completed

This is how board 2 is completed

Cutting process

The cut was made in the CNC Kingcut KX4060

Soldering process

The soldering was done on thursday night at the Fab Lab Veritas

Slow and careful

In order not to stains with tin the board 2, I took the process of welding more slowly

Modules and boards

Here we see the boards finished with their respective module before assembling

Tx front view

This shows the transmission module from the front

Tx back view

And so it looks from behind. I decided to put the female pins in the back so as not to remove the module every time I needed to program the board

Rx front view

This is the front view of the assembled receiving module

Rx back view

As with the previous module, the female pins are located at the rear, this was a last minute decision when soldering

Programing the boards

The final step was to program the cards. After many trial and error interactions, I was able to find the right parameters to establish the communication

Tx code

This is the test code for the transmitter. Basically what it does is send a number and turn on a led every few seconds to indicate that it is transmitting

Rx code

This is the test code for the transmitter. In this case simply turn on a led every time you received the number sent by the transmitter

Demo video

Click on the image to see a video of the system in action

Experience: Using L2C protocol

Objetive:

Implement and interpret networking protocols

Links:

I2C (master and slave) on the ATtiny85

Resources:

INO master code
INO slave code

Using the L2C protocol

When I saw this diagram of the L2C communication I thought that I physically only needed to join the SDA and SCL pins and that the rest was done with programming

SDA and SCL pins

In this drawing we can see which pins correspond to SDA and SCL in an Attiny85

Big mistake

So my boards were ready to connect to each other, but it never worked

Tx code demo

It was assumed that the transmitter code would send 3 visual effects to be executed in the LED of the receiver

Tx code demo

And every few seconds he would turn on his own led to indicate that he was constantly transmitting

Rx code demo

On the other hand the receiver would take the order of the transmitter (one at a time) and execute the visual effect on the red led

Rx code demo

The effects were simple: fade slowly, blink 10 times fast and blink 2 times and wait. But communication never worked

The solution

The solution was in the diagram shown by Neil where it is clearly seen that there must be a resistance of 10K between the pins and VCC

Testing the solution

So with the help of a breadboard I put the respective resistors that fortunately had at that moment

It worked !!!

After many hours of failed attempts and unsuccessful searches on the internet, the solution was always in front of my nose

Video demo

Click on the image to see a video of the system working