So for reasons I’m not entirely sure of myself I decided I was going to build a Farnsworth.

For those of you who are not fans of Warehouse 13, as Farnsworth is a Steampunkesque hand held video and audio communication device, named after Philo Farnsworth the inventor of electronic Television.

A picture of one from the TV series is viewable on the Warehouse13 fandom site here

Of course this is only a prop, me, being me wanted one that worked.

“The Farnsworth is a two-way audio and video communications device invented by Philo Farnsworth in 1929, soon after the invention of the television. They’re used by Warehouse agents because they are on their own secure frequency spectrum and can’t be cracked, hacked, tapped, or otherwise “broken.” However, Artie stated in Season 5 that it could potentially be vulnerable to hacks if Claudia messed with it.”

My Farnsworth, will be totally hackable, insecure and very easily broken, but working. (hopefully)

Of course I could have just put a phone in a box and extended the display, microphone etc. but where is the fun in that ?

I’ve been playing with Pi Picos a lot recently, and Id not really explored the Pi PicoW and its networking abilities.

So all I need to do is to attach a camera, a display microphone and speaker and I’d be ready to go. Oh, and I didn’t want it to cost me an arm and a leg.

Looking in my spares box I had a cheap camera the OV7670, the problem with this device is, although cheap, it uses 14 IO, this would severly limit what else I could do with the PICOW. Luckily UsedBytes( Brian Starkey) https://github.com/usedbytes/camera-pico-ov7670 had done a pico project for robot vision using this camera, for this he had used a parallel to serial shift register to drop the 8 data lines to a single line and the PIco’s PIO to reconstruct the data. The downside was his library only ran at 80×80 pixels in mono.

After quite a lot of changing parameters in his library I got it to work dropping a 240×320 colour (RGB565) image into the Picos ram.

The Display was much easier, the GC9A01 35mm circular display is much more common, and as all I needed was to be able to write bitmaps to the display, I soon had cut down the available librarys and had a DMA running to drop the camera image to the display.

As I only wanted 240×240 on the display, I split the process into lines, rather than moving the whole buffer at once.

This also meant that I could send this data easily to a UDP Socket on the PicoW. All I do is add the line number to the beginning 240 RGB565 integers, and send this as a UDP packet.

At the receiving end, I strip off the first byte and dump the rest directly into the display. If a line is missing or corrupt (this is UDP) it gets over written in 1/5 second anyway.

This scheme also left me with 241-255 as a starting byte I could use for other purposes. Sound being one of these.

Sound is via a single transistor amp (probably needs to be a better amplifier) into the pico’s A2D sampled at 8Khz

So sound is given a starting byte of 250 and 10mS of sound is sent in the same way a line is sent every 10mS

At the other end the sound packet is unpacked and pushed into a FIFO buffer so it plays for 10mS, if the buffer empties then silence is played.

The Case outer is 3d printed from black PLA, and the two front plates are made from black acrylic engraved on a laser cutter with infill of acrylic paint.

Loads still to do, Ill update here as the project progresses.

The code is available on Github https://github.com/ExtremeElectronics/PhiloFax

Continued here…

A Pico Emulated Camputers Lynx

The Camputers Lynx was a classic, although not massively popular computer in the early 1980’s. It featured a z80 at 6Mhz and full colour graphics, with none of the BBC micro’s (or others) Graphics mode shenanigans. And for its time many advanced capabilities like 96K memory, a disk system (later upgradable to CP/M 80), and a proper keyboard. Unfortunately it hit at a bad time, the Spectrum was much cheaper, but much less capable, and the BBC was being pushed massively by the BBC (unsurprisingly). It’s eventual down fall was that its brilliant graphics were both quite slow and due to its strange memory banking system, rather hard to program. Eventually it lost out due to the lack of game titles compared to the Spectrum and BBC Micro/Electron.

But I had one and I loved it (latterly I had three)

I already have a PCB that Ive used for Pico Emulation of a number if things, so that was my go to as a start.

I had asked for permission to use the code by Charles Peter Debenham Todd retrogubbins (as there is no licence on his GitHub pages) and he graciously let me use his code with no restrictions.

I based my Pico design on his PALE emulator and his ESP 32 emulator https://github.com/retrogubbins/PaleESP32VGA

One of the first issues I had was that the Z80 emulation that he used did not have any licence either, so early on I swapped it to LIBZ80 © Gabriel Gambetta (gabriel.gambetta@gmail.com) 2000 – 2014 which is currently maintained by EtchedPixels as part of the z80 emulation kit https://github.com/EtchedPixels/EmulatorKit

I’ve used this library before in the RC2040 So familiarity was on my side too.

Swapping over the emulator and porting the ESP32 code to the Pico was amazingly straight forward, I needed to write some code to DMA out the RGB banks to a display (240×320 OLED) and I quickly got a Lynx prompt.

Unfortunately it was in Yellow, and the emulation stopped there. I took me a while to get past this, until I realised that the Lynx Beeps, between writing the Red and Green banks, and before writing Blue. I hadn’t implemented the code for the sound / speaker.

Adding this in gave me not only a while logo, but two power up beeps, and (after spanering in serial to the keyboard emulation ) a workable basic.

So time to make a case.

I took the measurements from a real Lynx and scaled it to roughly fit the keyboard I had with the PicoPuter. It came out as roughly 1:3

Of course Not everything fitted correctly, so after a few goes.

I got one that fitted and held the PCB’s in roughly the right place.

Of course I needed a monitor, so I did a quick 3D print of an IBM 5151 style monitor. This gave me the space to the right to hide the display connector. and as the original was only 12″ didn’t look out of place with the small Lynx Case.

For the keyboard I wanted actual working keys.

So I made an escutcheon from grey sprayed card

and laser cut/engraved a set of small keys to fit. Because I couldn’t get grey acrylic I used transparent acrylic, on top of a grey sprayed key holder.

The effect is grey keys with white painted idents.

Not 100% happy with these, but I have a set for working grey keys, on a grey Lynx shaped case. For a more accurate layout I’d need a custom Lynx keyboard PCB.

The whole case is only 120mm wide to give you some idea of scale.

The two PicoPuter PCB’s sit inside and a small battery, because it was vital for this to run as a portable 🙂

The Ribbon cable is the feed to the display, which is mostly hidden by the case and the display itself.

and attached to the back of the display by a small daughter board.