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by mahjongg
Thu Nov 15, 2018 5:50 pm
Forum: Off topic discussion
Topic: My own Retro homecomputer called RhoCoCo
Replies: 22
Views: 463

Re: My own Retro homecomputer called RhoCoCo

Then if I do return to using a real Z80, I must give the memory mapping problem (supporting 128K RAM) some more thought, because I'm getting more and more convinced that some hardware support for it is unavoidable. Bank switched memory was not unheard of even for early S100 bus microcomputers. I wo...
by mahjongg
Thu Nov 15, 2018 5:19 pm
Forum: General discussion
Topic: Pi Model 3b and 3b+ power failure
Replies: 6
Views: 133

Re: Pi Model 3b and 3b+ power failure

There is just one scenario I can think of that could cause this, (except from two conductors inside the microUSB power connector that have come loose, and are shorting out) and that is that your original supply over-volted the PI with 6Volt or more. That would trigger the over-voltage protection dio...
by mahjongg
Thu Nov 15, 2018 1:50 pm
Forum: Off topic discussion
Topic: My own Retro homecomputer called RhoCoCo
Replies: 22
Views: 463

Re: My own Retro homecomputer called RhoCoCo

It seems the "imminent arrival" of the Propeller 2 has gone on forever, and I'm not planning to wait for it. Obviously it might be interesting for a successor of the rhococo, and i'm certainly keeping an eye on it. However, in any case, it wont be a (40-pin) DIP chip, and so wont fit into my current...
by mahjongg
Thu Nov 15, 2018 1:38 pm
Forum: Troubleshooting
Topic: 5 volt GPIO power pins broken
Replies: 6
Views: 187

Re: 5 volt GPIO power pins broken

If you connect more than 4V (3V3 + one diode forward drop) to a GPIO pin then this can cause latchup in the area of the chip occupied by the GPIO electronics of that pin, this will cause an internal short inside the chip, that will rapidly spread through the chip, and the transistors through which t...
by mahjongg
Thu Nov 15, 2018 1:31 pm
Forum: Troubleshooting
Topic: Ground pi 3 to earth
Replies: 3
Views: 64

Re: Ground pi 3 to earth

True, the USB power supplies used with raspberry PI's are normally double isolated types. When the PI is used with a (HDMI) monitor the PI will normally be grounded through the HDMI cable (if the monitor is indeed grounded, as it should). You can connect any ground pin or point of the PI to an earth...
by mahjongg
Thu Nov 15, 2018 10:28 am
Forum: Off topic discussion
Topic: My own Retro homecomputer called RhoCoCo
Replies: 22
Views: 463

Re: My own Retro homecomputer called RhoCoCo

I am not 100% sure that the z80 is simpler than the ARM? The z80 has more instructions, is less orthogonal, and has seperate address space for I/O (if one chooses to use such). The ARM has a ver orthogonal instruction set (we use the same move or load/store instructions to return from a subroutine ...
by mahjongg
Thu Nov 15, 2018 10:11 am
Forum: Off topic discussion
Topic: My own Retro homecomputer called RhoCoCo
Replies: 22
Views: 463

Re: My own Retro homecomputer called RhoCoCo

I'm not afraid there will be any confusion between the Tandy Color Computer, (nicknamed coco) and my Retro Home color computer (rhococo), but I agree that the similarities in name went not unnoticed to me. On a side note, I'm still doubting over whether using a second P8X32A (propeller chip) is the ...
by mahjongg
Wed Nov 14, 2018 5:33 pm
Forum: General discussion
Topic: Does the PI Zero run Centos or Debian?
Replies: 11
Views: 343

Re: Does the 0 run Centos or Debian?

Yes. They were the guys that made the 2900 series of bit slice processor chips and then the 29000 RISC processors. Sadly they gave up all the good RISC stuff and started copying some other fly by night companies instruction set. Luckily they eventually invented their own 64 bit instruction set and ...
by mahjongg
Wed Nov 14, 2018 5:23 pm
Forum: Off topic discussion
Topic: My own Retro homecomputer called RhoCoCo
Replies: 22
Views: 463

Re: My own Retro homecomputer called RhoCoCo

Using the PI's GPU as a "simple and understandable system" does not make sense to me, its the most incomprehensible part of an RPI's SoC, and the only "black box" like part of the system. It is "black box" by intent and lack of disclosure but the lid has been lifted enough to allow it to be easily ...
by mahjongg
Wed Nov 14, 2018 5:15 pm
Forum: Off topic discussion
Topic: My own Retro homecomputer called RhoCoCo
Replies: 22
Views: 463

Re: My own Retro homecomputer called RhoCoCo

Yeah, I know, but I can't buy any 6502 compatible processor in DIP form from any of my common suppliers, and yes I have looked for them. They seem to be not as commonly used as the Z80, and I fear for their future availability. The Z80 can be bought from Farnell, for about 5 euro, and the Propeller ...
by mahjongg
Wed Nov 14, 2018 3:31 pm
Forum: Off topic discussion
Topic: My own Retro homecomputer called RhoCoCo
Replies: 22
Views: 463

Re: My own Retro homecomputer called RhoCoCo

Using the PI's GPU as a "simple and understandable system" does not make sense to me, its the most incomprehensible part of an RPI's SoC, and the only "black box" like part of the system. There are only a few people in the world that can understand its vector based GPU instruction set well enough to...
by mahjongg
Wed Nov 14, 2018 1:30 pm
Forum: Off topic discussion
Topic: My own Retro homecomputer called RhoCoCo
Replies: 22
Views: 463

Re: My own Retro homecomputer called RhoCoCo

The "8-bit guy", well know from his you-tube Retro computer vlogs, ( https://www.youtube.com/channel/UC8uT9cgJorJPWu7ITLGo9Ww ) described his wish for his "dream computer" thus: Why not use the Raspberry Pi? Well, to be honest the Raspberry Pi is just a linux computer. You cannot program the Raspber...
by mahjongg
Wed Nov 14, 2018 10:29 am
Forum: Off topic discussion
Topic: My own Retro homecomputer called RhoCoCo
Replies: 22
Views: 463

My own Retro homecomputer called RhoCoCo

As a few people may know, I have been working on my own 8-bit retro computers for some time now, my first attempt was a ZX81 clone I called ZX81+34, and I wrote about it earlier here: https://www.raspberrypi.org/forums/viewtopic.php?p=551927#p551927, and published about it on my maker space wiki her...
by mahjongg
Tue Nov 13, 2018 5:10 pm
Forum: Media centres
Topic: Help with powering RPI 3b+ and 7" touch screen
Replies: 4
Views: 203

Re: Help with powering RPI 3b+ and 7" touch screen

It's simpler to find a 12v power supply than a 5.2V one (5.2v is odd, because standard USB is generally 4.85V, so any generic "5v" adapter will result in an undervolt Pi). "standard USB is generally 4.85V", is nonsense the standard is 5.00V, not 4.85V. But yes, all power supplies do have an percent...
by mahjongg
Mon Nov 12, 2018 5:10 pm
Forum: General discussion
Topic: What really is raspberry pi?
Replies: 6
Views: 307

Re: What really is raspberry pi?

One of the main things you have to know that the PI runs on an ARM processor, not on an Intel/AMD chip, its hardware therefore resembles more a smartphone or tablet than a classic desktop PC.
It means that it runs a version of Linux, rather than something else.
by mahjongg
Mon Nov 12, 2018 3:39 pm
Forum: Troubleshooting
Topic: How to fix a ripped wire?
Replies: 5
Views: 135

Re: How to fix a ripped wire?

I would not solder directly to the terminal, solder to the removed quick disconnect (faston) terminal instead. https://www.waytekwire.com/images/items/22-18GA-Female-Disconnect-30516_f.png The plastic of the blade terminal of the button is probably made from a kind of plastic that melts when you add...
by mahjongg
Mon Nov 12, 2018 10:02 am
Forum: Advanced users
Topic: Pi Zero's on board 3.3V supply
Replies: 5
Views: 178

Re: Pi Zero's on board 3.3V supply

Look at the schematic of the Zero, which can be found here: https://www.raspberrypi.org/documentation/hardware/raspberrypi/schematics/README.md it shows the dual regulator, a chip with a name starting with PAM.... look up its datasheet, and it will tell you how much current the device can deliver, n...
by mahjongg
Sun Nov 11, 2018 2:33 am
Forum: Troubleshooting
Topic: Cannot boot NOOBS.
Replies: 12
Views: 283

Re: Cannot boot NOOBS.

no raspberry pi can boot from an EXFAT partition, a FAT32 (or FAT16) partition is required. meaning that after formatting it regularly, (to remove all partitions) you have to re-format it to FAT32. using Etcher is simpler, as formatting is not required, as imaging will overwrite it anyway. as always...
by mahjongg
Sat Nov 10, 2018 9:30 pm
Forum: Automation, sensing and robotics
Topic: Read Temperature from Omron K3MA
Replies: 5
Views: 168

Re: Read Temperature from Omron K3MA

You might not like this, but IMHO Rattus is right, the device does not seem to posses any kind of digital interface, see https://assets.omron.eu/downloads/manua ... ual_en.pdf
by mahjongg
Fri Nov 09, 2018 6:54 pm
Forum: Other projects
Topic: Introducing Pi386
Replies: 15
Views: 565

Re: Introducing Pi386

You say PI386 is something new, but this: https://www.youtube.com/watch?v=x5-vVgkj8UU was shown two years ago, what is the difference between it, and "PI386"? :mrgreen: where is the emulation step to execute x86 CPU instructions on the PI's ARM CPU actually happening, not in WINE, Wine is Not an Emu...
by mahjongg
Fri Nov 09, 2018 10:28 am
Forum: Raspbian
Topic: Duplicate an image using Win32DiskImager doesn't work
Replies: 13
Views: 362

Re: Duplicate an image using Win32DiskImager doesn't work

SD-cards always have multiple non working sectors, so "identical sized" cards, are never exactly the same size.
by mahjongg
Fri Nov 09, 2018 10:17 am
Forum: General discussion
Topic: Raspbian and RetroPie on same SD card?
Replies: 3
Views: 115

Re: Raspbian and RetroPie on same SD card?

Retropie is an application. it can be installed on Raspbian, or comes pre-installed as a complete image.
by mahjongg
Thu Nov 08, 2018 3:06 pm
Forum: Beginners
Topic: More than one connection to gpio and speaker/mic problem
Replies: 9
Views: 170

Re: More than one connection to gpio and speaker/mic problem

The PI does NOT have any audio input hardware.
Common solutions, an USB or I2S microphone.
by mahjongg
Thu Nov 08, 2018 2:58 pm
Forum: Troubleshooting
Topic: Only the red LED is active, Pins don't work
Replies: 3
Views: 84

Re: Only the red LED is active, Pins don't work

Could be the 3V3 supply, which is known to be "temperamental". Some people reported a sudden fail of the 3V3 supply, but that was after a short. But Its also possible your fan introduces inductive spikes on the 3V3 that have the same effect as shorting the 3V3 supply. How is the fan powered by the P...
by mahjongg
Thu Nov 08, 2018 1:16 pm
Forum: Advanced users
Topic: relay 220ac light
Replies: 31
Views: 482

Re: relay 220ac light

kecinotrab wrote:
Tue Nov 06, 2018 7:19 pm
Thank you all for your replies. I will invite electrican to do that.

Just in case. I made image of finall circuit. Is it right?
Not for a BC547 transistor, which has this pinning:
BC547 pinning.PNG
BC547 pinning.PNG (27.35 KiB) Viewed 59 times
Emitter and collector are swapped.

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