If you don’t know about Pocket C.H.I.P, then firstly, where have you been? And secondly, check out getchip.com
Assuming you have one, and assuming you have an RC2014, I’m sure you’re wanting to connect them together. Well, good news… it’s easy!
To begin with, open the Terminal and download Screen;
sudo apt-get install screen (Default password is chip)
The biggest “gotcha” is that the internal serial port service needs to be turned off, otherwise it just spews stuff. To do this,
sudo systemctl stop serial-getty@ttyS0.service
(Have a look at this article on more info about that)
Then start screen
sudo screen /dev/ttyS0 115200
The connectors on the top of the Pocket C.H.I.P are those nice offset ones that will take a strip of straight header pins and hold it there (Thanks NextCo!), so plug in a 4 way header to the very right, and connect Ground, UART:TX, UART:RX to the RC2014.
And that’s it! You’re good to go!
So, all the way back in deepest darkest December, I announced I would enter the Retro Challenge 2016 competition that ran throughout January. Those of you that followed by blog or Twitter account when I did this in 2014 will know that I blogged and Tweeted relentlessly for the whole month, but, this time around, almost nothing. Obviously, I’m keeping some secret about an amazing breakthrough or something, right? Well, truth is, I’ve done almost nothing.
Things started well, and on 1st January, I designed a new backplane for the RC2014. Although I hadn’t studied the circuit diagrams for the ZX81, Jupiter Ace or ZX Spectrum yet, I knew that there were resistiors between the Z80 CPU and other devices. The stripboard backplane I’d been using had served me well, but it was time to progress to a better solution, and one that could be adapted better to my needs. Knowing that PCB delivery times could be against me, I thought it best to crack on and get this ordered.
The basic circuit is very very simple – however, I wanted to get this just right, not only for Retro Challenge 2016, but for other possible RC2014 uses. Essentially, there are 8 40 way connectors that are linked straight through – however, the data lines and address lines for the leftmost 2 connectors and rightmost 2 connectors are separated by a pair of pads. These can either be shorted together for up to 8 commoned connectors, or have resistors soldered across them. I also added a power connector and the option of either running 5v directly in to the board, or regulating a higher voltage down via a LM7805.
So, the RC2014 is a great little computer. We all know that. However, to communicate with it, it is easiest to use the serial port and hook it up to a laptop or desktop PC. This makes detracts from the fact that it is small, portable and cheap as well as missing the point of running code on such a basic computer. So I’ve been looking for a solution to this.
Back when this was still running on a breadboard, I hooked up an Atmel ‘328 that was connected to a keyboard and 4 x 20 LCD display. It communicated with the RC2014 over the serial port and kind of worked ok, although 4 lines was very restrictive and the Atmel couldn’t really keep the screen running and listening at the same time. I have thought about using a ‘328 to drive a composite output, or maybe some kind of bigger LCD panel, but nothing really struck me as just right.
That is, until the kind people at Raspberry Pi released a cheap multifunction interface device a couple of weeks ago!
So, you may well remember that I entered Retro Challenge 18 months ago, and what a fun crazy busy time that was! Well, the January Retro Challenge competition is about to kick off in just over 2 weeks.
If you’re not familiar with Retro Challenge, shame on you! But you can de-shame yourself by heading over to http://www.retrochallenge.org/ and seeing what it’s all about. Essentially, it’s a month long bi-annual competition where the entrants set themselves a goal based around old school computing and blog, tweet and share their experiences. The goals are pretty loose, as long as they are based on something from last centuary (modern emulators of old kit is fine).
The challenge I set myself was to take a breadboard based Z80 computer and bring it to life in modular PCB form in such a way that I could spell out my name on. Have a look back through my blog to see how I did. Spoiler —->
Just a quick update to about the SD Bootloader I designed a few posts ago. Well, the PCBs have arrived and last week I took a soldering iron to one of them and gave it a quick test
One side of the board is effectively an Arduino, so without plugging it in to the RC2014, I connected up an FTDI lead and uploaded the Arduino Blink sketch. A quick check with a multimeter and one of the pins was altenating between 5v and 0v. So far, all good! (more…)
So, the RC2014 is great. I can run Microsoft BASIC and program it from there, and as long as I am using a terminal emulator, I can copy & paste to save and load programs. Alternatively, I can write Z80 code using an online compiler then download it, copy it to USB stick, move it to my old Windows 2000 laptop (which has a parallel port) so I can burn it on to EPROM to see if it works, make adjustments and repeat with another EPROM.
I will be the first to admit, however, that this is probably not the most efficient workflow. Not to mention the time and effort involved in wiping the limited stock of aged EPROMS.
So, I am in the process of designing an SD Card based bootloader.
My original plan had never been to design and build my own computer. I had, however, planned to build a clone of the Sinclair ZX80, which has been on my bucket list of things to own for year, and which I had found plans for online. Whilst collecting the parts and reading up on simple Z80 computers I got kind of sidetracked and ended up with the RC2014.
The heart of the RC2014 is a Zilog Z80 CPU, which is the same one that Sinclair used in the ZX80, ZX81, ZX Spectrum and Z88. If the ZX81 and ZX Spectrum can run a ZX Printer, then surely it follows that the RC2014 will be able to too?
I guess this is kind of a follow up to my Retro Challenge posts, as it was thoughts that stemmed from teaching myself Assembly Language for my Z80 project. Essentially it is a comparison between programming in the 70’s and today against building with Lego in the 70s and today.
But before I get stuck in, can you identify this famous TV family from a few crude Lego bricks? (more…)
Wow! What an awesome month July has been. The whole Retro Challenge thing has been great, and despite moments of stress or despair, I have thoroughly enjoyed taking part and seeing what everyone else has been up to. Before I sum up my project, I should make a few honourable mentions.
Retro Challenge – A huge thanks to Mark and Wgoodf do a great job in hosting this twice a year. Keeping everyone updated via Twitter has worked really well. Cheers guys!
Grant Searle is responsible for the general Z80 design I used and also converted MS BASIC from the Nascom to run on this. Really, this project is a test of my understanding of Grants work and seeing how far I can take things.
Nottingham Hackspace has an amazing “parts bin” that included the LEDs, Veroboard, case, some of the logic chips and the RAM I used.
OSHPark did a great job (for a very good price!) on the PCBs – even if the postal system did keep me on the edge of my seat for a bit!
Chris Gammell introductions to KiCad PCB design videos were critical in guiding me through the various stages of board design.
Rodney Zaks book Programming the Z80 has been like a bible for me. Combined with a few dozen other resources of Z80 info on line I’ve been able to at least get the basics assembly language programming.
CLRHome is a great online Z80 IDE that can compile assembly language in a variety of output formats including for the ZX Spectrum. I doubt I could have managed this in notepad!
All of the other Retro Challenge entrants deserve a mention too, but there’s a few that really caught my eye and taught me stuff about their particular approach to RC2014, such as Wgoodf – Turtles all the way down, Ians restoration of Northstar Horizon, Tezzas restoration and programming of Challenger 4P, John finishing work on Fahrfall
With over 24 hours to go before the end of July deadline the final piece of the puzzle fell in to place!
But, first, a quick catchup from the last blog post;