There’s an error in all of the the Sharp PC-1500 Technical Reference Manual versions I have come across so far: in the pinout of the 60-pin connector a pin is documented as being VBAT instead of F-GND. Your Sharp PC-1500 can be ‘killed’ if you short VBAT (Battery Voltage) to F-GND (Frame Ground).
If you look at the traces (here: taken from the Radio Shack PC2 Technical Reference Manual) you can see that pin 44 is connected to F-GND instead of VBAT. It is easy to verify this with a multimeter in continuity mode.
I have to admit that I also came across this ‘by accident’… so keep in mind to verify the documentation whenever possible. The corrected version of the 60-pin connector pinout should look like this:
Days are getting longer, and in the afternoons the temperature rises above 10°C… but if I’ve learned a lesson the last two years then that growing chilis and tomatos in our living room (although located on the south side of our house) is still far from enough for these seedlings…
So I’ve taken a few hours and built an LED grow light station for them. 😀
With now 6 Raspberry Pis lying (hanging) around inside and around my server rack I’ve started to look for a nice and clean way to mount them in my server rack. On thingiverse I’ve seen a few 3D printed Raspberry Pi brackets and I immediately liked the idea; but as I wanted a simple design with the ability to add a heat sink, I had to start from scratch. Also, at the time I started the design, there weren’t any brackets for the newest Raspberry Pi 4. So, the result of my effort can be seen here:
After a about half a dozen iterations over the last two months, the following 3D print is ready to be equipped with heat sinks and mounted in my server rack:
I’ve prepared two versions of the RasPi Rack holder, one for the the older Raspberry Pi 3 Model and one for the Rasperry Pi 4. The STL files for 3D printing are available for download and licensed under CC-BY-SA 4.0: RasPi_RackMount.zip
The heat sink was bought on ebay (link) and is the upper half of a passive cooled aluminium Raspberry Pi case.
The 2 HE rack panel was bought at Musicstore.de, but I’ve also seen them on ebay and Amazon. They also sell small panels to cover 1 or 2 empty slots, if necessary. The 2 HE panel can take up to 10 modules (i.e. Raspberry Pis).
The RasPi’s are currently all powered from the back side, each with their own power supply. I’m currently planning on inserting a 5x USB charger into one of the module slots to power up to five at the same time.
I’ve noticed that brute force is used in most of the videos on Youtube which show how to shuck the hard drive of a WD My Book. This isn’t necessary if you know where to apply pressure on the case. I’ve made a short video myself showing how to open the case without scratching it or breaking the tabs.
Don’t ask why but I find it interesting to grow plants others would consider to be weeds… which must be pulled out. This time (besides the obligatory Arabidopsis thaliana 😉 ) I’m cultivating Cardamine hirsuta (aka. hairy bittercress / Behaartes Schaumkraut). I’ve found it in our garden. Nice.
Got a few fidget spinners that were sorted out due to defects. Repaired most of them an played a little with them. In the end I did not have any use for a few dozen figet spinners so I donated them to a charity tombola…
But I kept a few of the LED circuits… just because they were blinking… you know…
I did not post anything for quite a while… we bought a house and moved into it. This consumed most of my spare time and my ‘hacking capabilities’ during the last few months. But the good news is: I’ve now got a whole room in the cellar which I’m currently turning into a hacker lair / electronics shop without having to care too much about the the WAF.
I just just returned from a business trip to the US and wanted to ‘report back’ with a nightly impression of New York / Manhattan. (Please forgive the low quality as the photo was taken with my smartphone from the airplane window.)
I’m currently working on a custom development board, based on a quarter of a century old microprocessor, the Sharp LH5801. This microprocessor is the heart of the Sharp PC-1500(A) Pocket Computer, also known as Tandy TRS-80 Model II.
I’ve got plenty of documentation on the processor and the Sharp PC-1500, but what I did not have was a spare processor to play with. Recently, I got hold of a dozen of them, so no excuse anymore for not playing with them. 🙂
I started the design process by measuring out the package size in mm and wondered about the strange results I got… Well the size of LH5801 package is – bang on – 0.7 inches. It also has an odd number of pins for such a package size: 76 pins. Both make it pretty impossible to use the standard footprints provided by various package libraries. At least a short round of googling for packages for Eagle CAD or KiCad was unsuccessful.
So I had to design my own footprint which was smoother than expected. I used a already present layout with the correct footprint pitch and adapted copied/adapted the pins.
The part was made with KiPart (based on a CVS table). The pin description and layout was taken from the Sharp PC-1500 Technical Reference Manual.