Networking & Communication

All the details about my communitiy internet Router can be found here. I am working on a cheap mikrotik routerboard and running a custom openWRT firmware on it. The Authentication server is based on Diameter, the captive portal is based on CoovaChilli. We went to SANOG32 to present our idea and right now 5 nodes has been running for about 6 months as our pilot project.
A key point in our network deployment is the dependence on the local Internet Exchanges. Since most of our users only use cached data services like Facebook and Youtube, the latency we have been able to provide has been better than any Telcos or ISPs operating in that area.

The Basic Selling point is Seamless internet experience for 3 hours in 5tk, that's 0.060 USD

Milestones Reached:

• 900 unique users reached, on our 5 nodes. Considering unique mac IDs.
• Average consumption of data is 684 MB download, 27 MB upload.
• Total Data consumed after setting up the four nodes is 5088 GB.
• Assuming the minimum price of 1 GB data from the telcos as 100tk, that’s about 610,560 BDT of data consumed by the users.
• We sold about 7000 5tk unlimited tokens, which is about 17 times cheaper than the average telcos and 94% of the price was slashed.

Back in 2015, I had the privilige to work for a weather balloon launch. I made a GPS tracking system for a weather balloon using a Radiometrix NTX-2b, a 433MHz RF transmitter. The mainboard was based on a raspberry Pi, the GPS device used was a Ublox-Neo 6. The onboard camera later recovered gave us some amazing footage. The vertical distance traversed was 32450.1 meters and the total displacement was 68.8km. The Communication device was able to keep track of it during the full journey while surviving extreme temperatures from - 25.312 Degree Centigrade to 40 Degrees.All the details about this project can be found here.

The Recieving Yagi Antenna was made using locally available materials such as copper rods and PVC sheets. Here are some of the notable data from the launch:

• Total Flight Time : 3 Hours 26 Minutes 41 seconds.
• Total ascend Time: 2 Hours 07 minutes 12 seconds.
• Total decent Time : 1 hours 19 minutes 29 seconds.
• Lateral Displacement : 68.8km
• Lowest recorded outside Temperature: - 25.312 Degree Centigrade
• Highest recorded Altitude : 32450.1 meters

Onboard Camera Recording:

I designed the board around the ADXL345 and the nRF240L01. As they required 3.3v power and we dont have logic level shifters at the lab, I used an atmega328p with an 8MHz resonator to run at 3.3v. I kept a seperate AMS1117 to power the nRF240L01 module as I read that they get a bit fussy if proper power is not supplied.

I used Sparkfun's ADXL345 breakout board as a reference for interfacing the ADXL345 chip. I tied pin 7 with VCC which enabled i2c mode and added noise filtering capacitors of 0.1uF and 10uF near the chip.

The board can be run on battery power as the voltage level needs to be just above 3.3 to work.

Important LibraryFunctions Used

• RF24 radio(7,8); [Used to initate the nRF module, CE/CS pins)


• byte addresses[][6] = {"1Node","2Node"}; [Assigning the addresses on the radios used]


• radio.begin();
  radio.setPALevel(RF24_PA_MAX); [Use RF24_PA_MIN if you don't have power regulation for the nRF module]
  radio.setDataRate(RF24_2MBPS); [define data rate]
  radio.setChannel(124); [set the channel to transmit the data to]


• radio.openWritingPipe(addresses[1]);
  radio.openReadingPipe(1, addresses[0]); [Open the writing and reading pipes, a bit like tx and rx in serial. Use alternating addresses in the recieve part of the code.]


• radio.stopListening(); [Stop listening before sending data]


• radio.write( &data , sizeof(int[3])) [Send 'data', an integer array of size 3 ]

I designed this board for our upcoming machine design project.
It has an nRF240L01 module connected on the SPI bus, header pins for the i2c bus, FTDI pinout and a connector for an HC-05 module which I will be using for this week's group work.

It has power management circuitry to drive two high current MG995 servos using LM2940 regulators. It also has two NDS355AN N- mosfets to control two 12v LED strips.

Important LibraryFunctions Used

• RF24 radio(7,8); [Used to initate the nRF module, CE/CS pins)


• byte addresses[][6] = {"1Node","2Node"}; [Assigning the addresses on the radios used]


• radio.begin();
  radio.setPALevel(RF24_PA_MAX); [Use RF24_PA_MIN if you don't have power regulation for the nRF module]
  radio.setDataRate(RF24_2MBPS); [define data rate]
  radio.setChannel(124); [set the channel to transmit the data to]


• radio.openWritingPipe(addresses[0]);
  radio.openReadingPipe(1, addresses[1]); [Using alternating addresses in this part of the code.]


• radio.startListening(); [start listening for data]


• radio.write( &data , sizeof(int[3])) [Send 'data', an integer array of size 3 ]

I'll just be using this board I made during the output week to read the data over i2c and print it on my Serial monitor. All details about this board can be found here.