• Utility Board

    John Whittington • 07/23/2017 at 11:48 • 0 comments

    Been a while since I've updated this. I'm using it lots though as a serial terminal and general embedded linux test bed. Makes an appearance with my Nixie Pipe  too: 

    Back to this project though: through using it I realised I had the wrong gender termination for a DTE (I had a DCE), which meant using nasty adaptors/null modem stuff. I replaced it with the correct, male DB9. It works well, because the utility GPIO DB9 is female, so there is no chance of connecting RS232 levels to the wrong port. 

    For the utility GPIO output, I also made a simple breakout board. The board includes headers for RX/TX, I2C, PWM and 5V/GND of the Pi, an LED status and most useful of all, a micro USB to power the WT-220. This means it can be powered like a standard RPi, rather than a DC jack. 


    Since I've had some enquires, I've added the WT-220 to my shop. Very limited numbers will be made and it takes quite a bit of time so it is priced accordingly. 

    https://shop.jbrengineering.co.uk/product/whitterm-220/

  • Build Photos and Video

    John Whittington • 05/22/2016 at 10:51 • 0 comments

    Bit of a break between updates but I've completed the first build and created video to demo the function of the terminal. Not much more to say, I'll let the video and photos do the talking.


  • Rear Panel and Teaser

    John Whittington • 04/16/2016 at 14:26 • 0 comments

    I've laser-cut the rear panel with engraving for I/O and a handy GPIO pin-out for the TTL DB9 output. I thought since I've got 6 spare pins I might as well connect them to the Pi GPIO for use with external projects. The engraving is filled with acrylic paint using a sort of silk-screening technique.

    Here's a teaser GIF of me running cool-retro-term on Arch :):

    I'm only awaiting the dual USB panel mount from China before I can complete the build. In the meantime, I'm comtemplating adding battery power...

  • Laminating

    John Whittington • 04/13/2016 at 19:10 • 0 comments

    Build is coming along. I've cut the layers on the laser-cutter and glued the sections together. I opted to use glue rather than a mechanical fixing like I have in the past due to the stepped sections and to create a seamless design. The screen and Pi assembly is held from the rear on the 4th layer via the four mounting screws so can still be removed from the laminated layers. The final rear I/O layer will be held at the four corners with self-tappers.

    Visualising before glueing

    I'm using two super bright white LEDs in parallel on each leg, which I ground down (I have 5mm in my bits box) then hot glued into the acrylic layer.

  • RX/TX LED Buffering

    John Whittington • 04/08/2016 at 13:25 • 4 comments

    I want the acrylic layer to be illuminated but also to act as a serial activity indicator. To ensure that the line signal does not deteriorate, I'm using a op-amp voltage follower as a buffer to drive the LEDs. I've also include a GPIO line to force the LEDs on and disable the activity indicator in-case it is annoying.

    Here's a link to the simple circuit on Falstad: Op-amp buffer

  • Fusion 360 Assembly

    John Whittington • 04/08/2016 at 13:17 • 0 comments

    I've used this project to experiment with Fusion 360. On the whole it has been good, although I did run into a number of features I'm used to on other pro CAD packages that are missing. It seems more of a in development tool, where features are added at the request of engineers in desperation upon finding a tool missing!

    Each layer of plywood is a separate 'sketch', that I export to DXF for laser-cutting. The official RPi screen and RPi are a assembly from this guy: https://grabcad.com/library/raspberry-pi-7-display-1

    I've opted for the official screen despite being twice the price due to the flex cable connection allowing for a nice tight assembly. Having arrived I'm glad I paid the extra for what is a well engineered bit of kit. The stepped design is to minimise material usage but also aims to pay homage to an old terminal casing dropping around the CRT.

    Assembly is here: http://a360.co/1qxSz4C


  • Initial Concept

    John Whittington • 04/08/2016 at 13:04 • 0 comments