PERSEUS-9 homemade mobile 6502 computer

PERSEUS-9 is a die-cast aluminum housing mobile computer having dual 6502 CPU, 48 keys and 40 x 7 LED character display.

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In 2021, I built my own floating-point interpreter system on my PERSEUS-8 computer. However, this system required a serial terminal for input/output, which was somewhat inconvenient to use for programming and calculation whenever I wanted. Therefore, I have developed the PERSEUS-9, a mobile stand-alone computer that can run this system independently.
Its features are as follows.
(1) PERSEUS-9 will have a keyboard and character display on the chassis panel, which can be used to operate a home-made floating-point interpreter.
(2) PERSEUS-9 has dual 6502 CPUs, with the first CPU running the interpreter and the second CPU performing key and display I/O processing. The address mapping of the two CPUs should be the same to facilitate operation verification.
(3) PERSEUS-9 shall be a synthesis of PERSEUS-8, 6802 Serial Terminal, and Floating Point Interpreter CI-2 technologies respectively.

1. Main feature

Figure 1 shows the external appearance of the PERSEUS-9. The enclosure is a die-cast aluminum case with external dimensions of 262 mm x 182 mm x 55 mm.

Fig.1    Appearance of PERSEUS-9

The user interface consists of a 48-key keyboard and a 40 x 7 LED character display. The display has been expanded from the 96-character display of the 6802 Serial Terminal to a 280-character display. Power is supplied externally via 5V, 3A power adapter. External Ni-MH 1.2V battery x 4 operation is also possible. User programs are backed up by the built-in battery.

    Figure 2 shows the inside of PERSEUS-9. The board has a two-tiered structure, and in this photo PB1, in which the main computer including the 1st CPU and the terminal part including the 2nd CPU are mounted, is visible. PB2, where the key switches and LED modules are mounted, is hidden underneath. The back of the enclosure has a power connecter, three D-sub connectors for the serial interface, and a 26-pin flat cable connector for the parallel interface. On the right side, the power switch, RUN/HALT switch, terminal select switch, and display reset switch are provided.

Fig. 2    Inside of PERSEUS-9

2. Enclosure

The enclosure is a die-cast aluminum case HQ-26-18-6N manufactured by Takachi of Japan, which is used. This enclosure is designed to be waterproof and dust-proof for outdoor equipment, but this function is ignored. Although the panel has many openings due to the hole drilling process, it maintains sufficient rigidity. Figure 3 shows the drilling of holes for switches in the panel using a reamer. 3mm-thick red transparent acrylic sheet is used as the filter for the LED display part.

Fig. 3    Reaming work for enclosure

    Figure 4 shows the connector holes for the interface and the holes for the toggle switches drilled in the back and sides. Such square holes are drilled continuously with a 3mm-diameter drill, the holes are pulled out, and then finished with a file.

 Fig. 4    Enclosure backside

3. Dual CPU hardware configuration

The hardware block diagram of PERSEUS-9 is shown in Fig. 5. The schematic and the parts location figure are shown in the attachment file. In Fig. 5, the left half of PB1 is the main CPU section shown on pages 1 to 3 of the schematic, and the 1st CPU is IC21. This is the almost same as removing the DMA control section which uses toggle switches and LEDs to input addresses and data from the PERSEUS-8 circuit. The main CPU section implements and executes homemade floating point interpreter CI-2 in 8 kB PROM area. The 16 kB RAM space is the user program storage area for the interpreter and the system work area.

    The right half of PB1 in Fig. 5 is the serial terminal section including the 2nd CPU shown on page 4 of the schematic. The 2nd CPU runs the serial terminal system software CT-3 on a 2kB PROM. This is basically similar to the 6802 Serial Terminal, but PERSEUS-9 has 2.9 times more LED modules than the 6802 Serial Terminal, so the processing speed needed to be faster. Therefore, the MC6802 (1 MHz) CPU was replaced with a 6502A (2 MHz). This resulted in a 6502 (2 MHz) dual-CPU configuration for the entire PERSEUS-9. This is not a recent CPU configuration with many cores, but it is a configuration with a main CPU and an I/O CPU, which was common around 1980. The two computer parts have the same address mapping to facilitate hardware operation verification. For example, the ROM and flat cable of the terminal part can be replaced with the main part to verify the operation as a terminal.

4. Peripheral devices

In Fig. 5, PB2 consists of 48 key switch matrices and 35 5x7 dot 8-character LED modules (HCMS-2912) shown on page 6 and page 5 of the schematic. The data lines of the LED modules are connected in cascade. And all of these are connected to the 8-bit...

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Schematics of PERSEUS-9.

Adobe Portable Document Format - 612.96 kB - 04/22/2024 at 04:22



Example user program for calculating planet positions from orbital elements

Adobe Portable Document Format - 19.47 kB - 11/28/2022 at 06:51



Example user program for PERSEUS-9 (memory dump, input hex start address)

Adobe Portable Document Format - 12.91 kB - 09/16/2022 at 04:48



Right side of PERSEUS-9.

JPEG Image - 1.45 MB - 09/14/2022 at 08:15



PB1 wiring side of PERSEUS-9.

JPEG Image - 3.00 MB - 09/14/2022 at 08:07


View all 11 files

  • 2 × R6502A Microprocessors, Microcontrollers, DSPs / Microprocessors (MPUs)
  • 3 × MC68B50 Microprocessors, Microcontrollers, DSPs / IO Controllers
  • 5 × D2716-1 EPROM
  • 3 × HM6264BLSP-10L Memory ICs / Static RAM (SRAM)
  • 3 × MAX233CPP Interface and IO ICs / RS-232, RS-422, RS-423 and RS-485

View all 24 components

  • PERSEUS-9 project log

    Mitsuru Yamada08/11/2022 at 11:43 0 comments

    1. The article was first posted on Jul. 23, 2022.

    2. Revised on Aug. 11, 2022

        Added the parts location figure and a memory dump program by using CI-2 in the attachment. 

    3. Revised on Aug. 22, 2022

        For ease of reading, the chapter 3 "hardware configuration" was divided into "3. Dual CPU hardware configuration," , "4. Peripheral devices," and "5. Component placement,". and the chapter 5 "System software" was divided into, "7. System software configuration" and "8. Terminal section system software. 

    4. Revised on Aug. 25, 2022

        Added the video 2 as an example user program that accesses AD converter connected to the parallel interface of PERSEUS-9.

        And added the example user program ADC_02.pdf to the attachment.

    5. Addition on Sep. 14, 2022

        A photo of the switches on the right side of the enclosure and a photos of the test situation during board making were added to the attachment.

    6. Revised on Sep. 16, 2022

        Added description of memory configuration in Chapter 3 "Dual CPU hardware configuration".

        Added description of serial and parallel interfaces in the main CPU section to Chapter 4 "Peripheral devices".

        Replaced the memory dump program MEM_DUMP_03.TXT in the attached file with MEM_DUMP_04.TXT, which allows hexadecimal input of start addresses.

    7. Revised on Sep. 22, 2022

        Added to Chapter 9 "Results" that CI-2 on PERSEUS-9 could perform elementary function calculations, line number editing, FFT, etc. as on PERSEUS-8.

    8. Revised on Sep. 24, 2022

        Linked a new explanatory video to "input and modification of user programs" in Chapter 9 Results.

    9. Revised on Sep. 28, 2022

        Added the video 3 as "Simple programming example on PERSEUS-9" in Chapter 9 Results.

    10. Revised on Nov. 28, 2022

        Added the video 4 as "Loading a program from an external PC terminal, and execution of its program to calculate the position of the planet."  in Chapter 9 Results.

    11. Revised on Feb. 27, 2023

        Added video link to 'simple serial terminal' in chapter 4 Peripheral devices.

    12. Revised on Mar. 14, 2023

        Added Fig.5.1 of a homemade PROM programmer connected parallel interface in chapter 4 Peripheral devices.

    13. Revised on Mar. 20, 2023

        Added a link for video to introduce updating CI-2 the interpreter by using a homemade PROM programmer for Chapter 7.

    14. Revised on Mar. 24, 2023

        Added a link for the schematic of a homemade PROM programmer in Chapter 4.

    15. Revised on Apr. 28, 2023

        Added Figure 5.2 of PROM module EXTROM-2 in chapter 4 Peripheral devices.

        Added description of user program loading by the ROM module in chapter 9 Results.

    16. Revised on Aug. 01, 2023

        Added Chapter 9 "Program loading", and added a link of codes of the interpreter CI-2 version 2.0.0.

    17. Revised on Feb. 03, 2024

        Added a video and the project link of 'Telescope Mount Controller using PERSEUS-9' to Chapter 10.

    18. Revised on Apr. 22, 2024

        Modified the circuit of the enable input pin 6 of address decoder IC36 from fixed H logic to the CPU reset signal to prevent the RAM from going into the active state during the power shutdown sequence. 

        Changed the schematic in the attached file to the Jan. 5, 2024 version, applying MOD 1 above.

View project log

Enjoy this project?



Charles Stevenson wrote 09/29/2022 at 17:54 point

I love the binary voltage display LEDs on the AD converter! This project is marvelous!

  Are you sure? yes | no

Mitsuru Yamada wrote 09/29/2022 at 22:00 point

Thank you for your comment! I first built my own ADC almost identical to this one 43 years ago. I observed its behavior and was so impressed that it affected the rest of my life.

  Are you sure? yes | no

flip wrote 09/09/2022 at 11:50 point

This is a beautiful piece of craftsmanship!
Not only on the outside, but also deep on the inside, the interpreter code is very elegant as well.

  Are you sure? yes | no

Mitsuru Yamada wrote 09/11/2022 at 10:55 point

Thanks for reading at the article on my own interpreter as well. I was able to create a floating-point interpreter with hand coding, toggle switch input, and manual debugging, without using a PC development environment. I don't think anyone would attempt something like this today. The interpreter is self-taught, but I learned a lot.

  Are you sure? yes | no

epooch wrote 07/30/2022 at 03:10 point

Another beautiful build! This enclosure is also sold under the brand name Gainta, model HQ033S in Europe or BUD IPS-3933 in U.S., if anyone is looking for it.

  Are you sure? yes | no

Mitsuru Yamada wrote 07/30/2022 at 04:23 point

Thanks for the information. Many of the aluminum die-cast cases on the market are thick-walled and very heavy at a certain size, but I was able to get one with just the right dimensions and not too heavy, so I used it for this project.

  Are you sure? yes | no

koko484005 wrote 07/28/2022 at 04:40 point

i like this invention

  Are you sure? yes | no

Mitsuru Yamada wrote 07/28/2022 at 04:54 point

Thank you! I have synthesized in my own way the basic technologies that are universal in the age of computer for hardware and software.

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Dan Julio wrote 07/28/2022 at 04:05 point

Spectacular, as always, Yamada-san.  Very nice build.  I like the round keys.

  Are you sure? yes | no

Mitsuru Yamada wrote 07/28/2022 at 04:47 point

Thank you for your comment!  I used many LED modules, I had to take various difficulties such as countermeasures against malfunctions caused by write signal pulses and speeding up the firmware. I think round keys goes well with the retro and futuristic design image combined with the aluminum die-cast case.

  Are you sure? yes | no

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