Help needed connecting the Next board UART to a PC RS232 serial port

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PiyoTaro
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Re: Help needed connecting the Next board UART to a PC RS232 serial port

Post by PiyoTaro » Mon Jan 28, 2019 9:38 am

  • supplement (2019/4/25).
    I made this post as an image of the "RaSCSI" project.
    It connects PiZERO's GPIO interface to a SCSI connector and emulates peripherals.

    It is necessary to convert the voltage of "SCSI bus" to that of GPIO, but there are methods such as voltage division by using resistors or voltage conversion logic ICs. I think that it is a project that is known to be localized to various people, such as termination impedance.
---

General questions about user hardware work

1. I would like to know the "Edge Connector" of 'ZX Spectrum expansion bus' and the standard of cartridge size.
2. Is the expansion bus of 'ZX Spectrum Next' the same standard as the conventional ZX Spectrum such as power capacity and "audio input" pins for example? (unpublished)

3. My opinion. Rather than designing a circuit such as an "address decoder" to produce an extension unit using a microcomputer or an interface chip, it would be more expensive to directly connect a microcomputer to the ZX bus.
For example, if you monitor the ZX bus with 'Raspberry Pi ZERO(or A+)' GPIO and make software for "expansion unit emulator" is inexpensive and versatile?
Last edited by PiyoTaro on Thu Apr 25, 2019 11:35 am, edited 1 time in total.

Alcoholics Anonymous
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Re: Help needed connecting the Next board UART to a PC RS232 serial port

Post by Alcoholics Anonymous » Mon Jan 28, 2019 6:38 pm

PiyoTaro wrote:
Mon Jan 28, 2019 9:38 am
1. I would like to know the "Edge Connector" of 'ZX Spectrum expansion bus' and the standard of cartridge size.
2. Is the expansion bus of 'ZX Spectrum Next' the same standard as the conventional ZX Spectrum such as power capacity and "audio input" pins for example? (unpublished)
The expansion bus is being looked at now so I can't really answer definitively. At the moment the expansion bus is a 128k bus. Available power supply is +5 and +9 only

The only audio io is EAR and MIC via the 3.5mm jacks.

There are also various internal headers for other things.
3. My opinion. Rather than designing a circuit such as an "address decoder" to produce an extension unit using a microcomputer or an interface chip, it would be more expensive to directly connect a microcomputer to the ZX bus.
For example, if you monitor the ZX bus with 'Raspberry Pi ZERO(or A+)' GPIO and make software for "expansion unit emulator" is inexpensive and versatile?
The next already has an internal header for connecting a pi; this configuration is known as the "accelerated" version and some number of backers will be getting it. Others can install a pi themselves.

How it will end up interfacing to the next is not final yet. Originally it was going to be a graphics accelerator -- essentially it would generate the video and the next would just send instructions to the pi. That was changed in favour of making a real computer so all that functionality is now in the fpga. Then it was used as a secondary display device called TK-Pie. The pi would snoop the z80 bus and watch for writes to the ula display ram and produce an hdmi display from that. I think that's how the ZX-HD device works. But using a pi that way really damages its performance and would make it difficult to install linux on it with this functionality, eg. It would also only be able to display the ula screen and not sprites, layer 2, etc. So now things like spi, i2c and a uart are being considered where you can asynchronously communicate with the pi and the pi itself can truck along without spending its time monitoring the z80 bus.

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xc8
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Re: Help needed connecting the Next board UART to a PC RS232 serial port

Post by xc8 » Tue Jan 29, 2019 10:11 am

Alcoholics Anonymous wrote:
Mon Jan 28, 2019 6:38 pm
How it will end up interfacing to the next is not final yet.
for sure for now it serves as vaporware
+++
ATZ

Ped7g
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Re: Help needed connecting the Next board UART to a PC RS232 serial port

Post by Ped7g » Tue Jan 29, 2019 10:37 am

xc8 wrote:
Tue Jan 29, 2019 10:11 am
Alcoholics Anonymous wrote:
Mon Jan 28, 2019 6:38 pm
How it will end up interfacing to the next is not final yet.
for sure for now it serves as vaporware
I have my pledge for cased+accelerator, but since it lost direct access into Z80 memory (due to stability/timing issues IIRC?), I'm far less interested. Any serial communication with Next machine will be far away from the evil things one would be capable to do with direct access into the machine, so with such paradigm shift I think I will expect it to become some kind of external harddrive and linux server, but using it directly in some app doesn't sound as attractive any more (one thing is the limited user base who will have accelerators fitted on their board, and second thing is this indirect usage of Pi board).

Alcoholics Anonymous
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Re: Help needed connecting the Next board UART to a PC RS232 serial port

Post by Alcoholics Anonymous » Tue Jan 29, 2019 3:37 pm

xc8 wrote:
Tue Jan 29, 2019 10:11 am
for sure for now it serves as vaporware
Vaporware means it doesn't exist and that's not the case :) They are attached to boards and are being experimented with.
I have my pledge for cased+accelerator, but since it lost direct access into Z80 memory (due to stability/timing issues IIRC?), I'm far less interested. Any serial communication with Next machine will be far away from the evil things one would be capable to do with direct access into the machine
This is really about finding a primary purpose for the pi. Right now that seems to be having it available to run development tools on the pi for sending programs to the Next, as well as having the Next available as a terminal for users to have easy access to a pi machine. Having uart, spi, i2c there also opens up the possibility of using pi hats which are plug-in modules that are intended for pis (don't ask me; I'm not an expert on the pi).

That doesn't mean that's the end of it. Having the pi monitor the z80 signals to respond as a device or snoop at what is going on really cripples the pi, though it may be something you want to do anyway just to be evil.

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varmfskii
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Re: Help needed connecting the Next board UART to a PC RS232 serial port

Post by varmfskii » Tue Jan 29, 2019 4:53 pm

As for the Pi as an accelerator, think about the tube interface accelerators for the Beeb. The tube connects the accelerator and the main machine through a few "ports" (the 6502 uses memory mapped rather than port I/O). This isn't really all that different from conencting using one of the standard interfaces of the Pi to communicate between the Pi and ZX Next.
Backer #2741 - TS2068, Byte, ZX Evolution

Alcoholics Anonymous
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Re: Help needed connecting the Next board UART to a PC RS232 serial port

Post by Alcoholics Anonymous » Tue Jan 29, 2019 8:57 pm

Yes this would be a first step so that people can use the pi immediately when they get their cased machines. And it's not a superficial use either - you get access to a pi machine as terminal as wel as being able to shuffle data back and forth, the main one being able to use the pi as a development platform for the next.

The time is getting close for manufacturing so I don't think there is much time left for core development before the cased are shipped. Keep in mind that the first step will be to burn the cores to flash on the bare boards which are already sitting complete at SMS. The core will continue to develop after shipping until the all the roadmap items are met. I expect we will have more participation from the community at that point.

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Pgartside
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Re: Help needed connecting the Next board UART to a PC RS232 serial port

Post by Pgartside » Wed Apr 24, 2019 9:53 pm

If you wanted to do a 3D game you could pass all the geometry to the PI then you will just need to pass in the players and enemies 3d coordinates with there direction of travel. The pi would use a physics engine to move the players and enemies, it could then pass back the new 3D location for everyone and send back a screen definition file from the point of view of the camera so it can be drawn on the pi screen.

PiyoTaro
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Re: Help needed connecting the Next board UART to a PC RS232 serial port

Post by PiyoTaro » Thu Apr 25, 2019 12:08 pm

    • UART
      https://specnext.dev/wiki/UART
      • here are some limits:
        Data format is fixed to 8N1: 8 data bits, no parity bit, one stop bit.
        No handshake signals, such as RTS/CTS, DTR/DSR.
        Not 5V tolerant. Putting more than 3.6V will cause the Spartan6 death
    • UART TX $133B
      Write to this port sends the byte to serial port (routed to WiFi module connector). Read from this port returns 0 if there are bytes to read in RX FIFO buffer, or 1 if no RX data.
    • UART RX $143B
      Reads data from serial port. Write to this port sets the speed of serial communication, see the table:
      0 = 115200 (default at reset) 1 = 57600 2 = 38400 3 = 19200 4 = 9600 5 = 4800 6 = 2400
https://www.facebook.com/groups/specnex ... %22R%22%7D
It seems that this thread was introduced by FB, so please ask me a question.

Is the baud rate of the UART that can be handled from the Z80 side limited to 115200?

https://www.facebook.com/groups/specnex ... %22R%22%7D
I also saw post such as the UART can tolerate 31.25 Kbps, so it can also handle MIDI.
The audio decoder chip "VS1053b" has a stand-alone mode that can be used as a GM2 compatible MIDI instrument. I saw a lot of modules that adopted VS10x3 chip as "mp3 decoder", I want to see a MIDI demonstration.

appendix
"DIY VS1053 MIDI Sound Module" (YouTube by Mike Rainbow 2019/01/28) https://youtu.be/7xIEA66e7eI
""Adafruit "Music Maker" MP3 Shield for Arduino-New Products 4/9/2014"" (YouTube: Adafruit Industries 2014/04/10) https://www.youtube.com/watch?v=ZsjDlnBgfTg&t=241s

Postscript. I added a supplement to my past post.

Alcoholics Anonymous
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Re: Help needed connecting the Next board UART to a PC RS232 serial port

Post by Alcoholics Anonymous » Mon May 27, 2019 5:11 pm

PiyoTaro wrote:
Thu Apr 25, 2019 12:08 pm
Is the baud rate of the UART that can be handled from the Z80 side limited to 115200?
No, up to 2Mbps is being used by current development tools. The baud rate can be set in fine steps.

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