This page holds all the files necessary to make the VAYU-NTX v1.04 PCB and firmware code for the ATMEGA328P AVR Device. The design is released under Creative Commons Attribution – Non-Commercial – Share Alike. This means you may distribute this design with credit to the creator, modify it but it must not be used for commercial gain. Any modified version should also be made available freely.

This design is a development of the VAYU v1.02 HAB Tracker but with a few differences. The RFM22b RF Transmitting module has been replaced by the more stable Radiometrix NTX2b and the uBlox NEO 6M GPS unit has been replaced by a smaller uBlox MAX7 unit. The design was made specifically to break out as many pins from the ATMEGA328P as possible in as small a pcb that could be designed. There are also expansion boards that plug into the 16-pin header planned. One for Temperature/Humidity measurements and another for general prototyping.

PLEASE NOTE Because VAYU-NTX runs on an 8MHz Crystal (to save power) it requires programming as an 8MHz board with the Arduino IDE (The firmware code is Arduino specific). The first step is to load the bootloader to set the fuses correctly, despite the bootloader being overwritten when the firmware is loaded and is not used. Do this by setting the board in the menu, the type of programmer and then Burn Bootloader. Carry out this process after adding the custom text below to your boards.txt file. I would recommend making a backup of the file prior to editing. You can edit it in a program such as Programmer’s Notepad or Notepad++ Be sure to restart the Arduino IDE software after this for the entry to show up in the menu.

Within the Arduino IDE directory structure, there is a file called boards.txt (X:\arduino-XX.X\hardware\arduino\avr\boards.txt on my PC). This requires a custom entry of which an example is shown below.

##############################################################

vayu.name=VAYU-NTX (3.3V, 8 MHz) w/ ATmega328
vayu.upload.tool=avrdude
vayu.upload.protocol=arduino
vayu.upload.maximum_size=30720
vayu.upload.speed=57600

vayu.bootloader.tool=avrdude
vayu.bootloader.low_fuses=0xFF
vayu.bootloader.high_fuses=0xDA
vayu.bootloader.extended_fuses=0x05
vayu.bootloader.file=atmega/ATmegaBOOT_168_atmega328_pro_8MHz.hex
vayu.bootloader.unlock_bits=0x3F
vayu.bootloader.lock_bits=0x0F

vayu.build.mcu=atmega328p
vayu.build.f_cpu=8000000L
vayu.build.board=AVR_UNO
vayu.build.core=arduino
vayu.build.variant=eightanaloginputs

##############################################################

I have placed this entry beneath the entry for the UNO. This ensures the Arduino IDE sets the speeds correctly. I believe the important line is “vayu.build.f_cpu=8000000L” which ensures the Arduino IDE sets the speeds correctly when interpreting the firmware.

Full physical design files are available lower down on this page.

[UPDATE 19-11-2013]

Having spent some time in #hackvana IRC channel, I was recommended to obtain a PCB Fixture Block from Arachnid Labs to help with applying solder paste to boards. I have ordered the smaller of the two possible models and will review it when it arrives. Until then, I have updated the design files to be compatible.

[UPDATE 19-11-2013]

The boards have arrived from Hackvana. I’m very pleased with the consistent quality and the blue soldermask is really classy.

Here’s one of the boards assembled and demonstrating the blink program from Arduino. This prototype shows the switch position bridged after some troubleshooting was carried out but has now been replaced and working. During the process I heated the programming header a little too much too! The 100uH coil is a little large for this board so I will have to source an alternative component. I have also added the option of using a smaller SMD crystal (Package 5032) instead of the larger 49 sized component.

[UPDATE 20-11-2013]

After following instructions on Anthony Stirk’s blog, a small hardware modification and a lot of help from the #highaltitude guys (namely eroomde, fsphil and UPU) I managed to get VAYU-NTX sending a RTTY test sentence. The hardware issue was caused because I’d wired the NTX module’s TXD pin to the AVR pin PB0 which is not PWM capable. The solution was to cut this line and wire the NTX pin directly to a flying lead and connect it to PD3 on the expansion header. This issue has been fixed in v1.04 so the modification will not be necessary on future PCBs.

The next step will be to interrogate the GPS module and monitor the output.

[UPDATE 27-11-2013]
After wrangling with code from several sources and help from Andy Garratt M6GTG and Matthew Beckett, the code is sending telemetry.

[UPDATE 28-11-2013]
Having soak-tested the final version, I feel confident in releasing the design files. NOTE: If you receive an error upon loading the BRD and SCH files into Eagle concerning a duplicate layer called ‘Stencil’ you can safely ignore it:

To save the following files, right-click and save-as.

• VAYU-NTX v1.04 Eagle v6.3.0 .SCH file
• VAYU-NTX v1.04 Eagle v6.3.0 .BRD file
• VAYU-NTX v1.04 Gerber ZIP File
• VAYU-NTX v1.04 .ino file
• VAYU-NTX v1.04 Image files
• VAYU-NTX v1.04 Parts List
• VAYU-NTX v1.04 Circuit PDF

The entire directory of resources is available at VAYU-NTX v1.04

———————–

VAYU-NTX-th v1.0 – Through-Hole version

Using a similar circuit, I have designed a Through-Hole version of the PCB. There is no code to drive this version as yet although it should be pretty much the same as the SMD version. I have linked to the previous code below for convenience. The through-hole pcb makes use of a GPS module which is available from HAB Supplies. Just solder a header on the VAYU board and a socket under the GPS breakout board and it will sit neatly above. I won’t be fabricating the through-hole version and I can’t guarantee it will operate correctly. Use at your own risk. Full design files available below.

To save the following files, right-click and save-as.

• VAYU-NTX-th v1.0 Eagle v6.3.0 .SCH file
• VAYU-NTX-th v1.0 Eagle v6.3.0 .BRD file
• VAYU-NTX-th v1.0 Gerber ZIP File
• VAYU-NTX-th v1.0 .ino file
• VAYU-NTX-th v1.0 Image files
• VAYU-NTX-th v1.0 Parts List
• VAYU-NTX-th v1.0 Circuit PDF

The entire directory of resources is available at VAYU-NTX-th v1.0

I have received a lot of assistance whilst creating this design. I must especially thank Ed (from #High Altitude) and Anthony Stirk, for advising me on layouts. Also I owe a debt of gratitude to Chris Stubbs, Dave Akerman, Leo Bodnar, Matthew Beckett and all the great folk in the UKHAS community for their advice and support.

VAYU-NTX v1.04 & VAYU-NTX-th HAB Trackers by Steve Smith is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License.