New Method For DC Serial To SDCARD - InDevelopment

I love the Dreamcast, Its a very cool system to work with. But I dont like the Speed of data throughput on the SDCard interface.

So Im working on a New Interface device, using the same Serial port as the original SDCard interface. But with a big twist.

Heres what i got so far:

Using the MAX3100 UART to SPI chip (Operates on CMOS level logic), will be used injunction with a PIC18F2455 MCU. This MCU also has a native USB interface, could be handy in the future.

So i kinda works like this:
MAX3100 picks up the native signals put off by the dreamcast's serial port, which then converts them into a SPI output interface. From there the PIC will be intercepting the SPI on one of the two virtual SPI interfaces that it will have.

Next the PIC will perform the necessary functions and operations to read and write on the second virtual SPI output interface; That in-turn provides the data interface to the SDCard at speeds that can reach well over the Dreamcast's ~2MBps limit.

The USB port could function as a PC - DC debugger as well as an ISO loader.

The possibility's of the MCU on the Dreamcast's serial port, could allow well over 20+ GPIO for Custom hardware interfacing. This might require a faster more robust MCU, which i also have if necessary. Technically you could use the dreamcast as a Robots Main control Hub. Or some other crazy stuff. Pretty much like having a Dreamcast + Arduino combined.

Ill be posting updates as i go .

UPDATES:

Going to Switch to the PIC18F45K50 MCU. Working on pin mapping.

Possibly dropping the MAX3100.

 

Good luck seems interesting! Document your findings!

 

I dont understand how you are going to get any extra speed. Your Serial to SPI interface is still limited to the speed of the serial port on the dreamcast. You are still going to need to convert SPI back to serial data, that is still going to be decoded in the current manner, by the current software.

Could you explain where this speed up is supposed to be coming from?

 

it works the same way u can get 30Mbps with a DC ftdi USB coders cable, it all depends on the interface. Rs232 DB9 port for DC coders able is max of 117XXX bytes per sec.
im also aware there needs to be DC side software development to use this...

 

I'm also curious how to get a higher speed from a serial DC port. AFAIK, it all depends on the source of the signal, not on the interface...

 

You will always be limited by the Dreamcast serial interface though no? AFAIK, the limit is 12Mbit or 1.5MB/s. Serial SD cable can reach 400-500 KB/s.

 

Just because you can interface PC -> USB cable fast, doesnt mean USB cable (FTDI chip) -> DC will be that speed. Just having the option for faster baud rate doesnt mean the other side will accept it.

While you might be able to send data to the PIC faster, the PIC wont be able to relay that data to the DC that fast, as the DC serial port is the limiting factor.

 

apparently i miss understood the DC side of the Serial connection. Well ill aim for the dcs 1.5MBps max...
Ill keep you all posted

 

I like the idea of some general purpose IO on the serial port. If you could add some GPIO and SPI interfaces and get the support of Dreamshell, it will still be an interesting project.

Especially as the serial port is getting freed up with the IDE mod being able to boot dreamshell directly.

 

This is exactly my reason for this . I might just scrap the SDCard and add a full GPIO bank - with UART - SPI - I2C and atleast 30 total GPIO.

I have so many MCU's and ARM's to choose from idk what to use yet... i Switched Again from the PIC18F45K50 to the PIC18F4555.

Maybe some ADC's and more analog I/O

 

GPIO would allow very nice projects. Imagine removing the PSU, replace it with small modern dc-dc converters and use the extra space to put an internal vga-box with scanlines and maybe a hdmi converter. And then you boot an homebrew that can switch on/off the scanlines or change the video output via GPIO, etc. All that with a retail-looking console.

 

Omgosh! IDEA! With the native IDE Drive interface already discovered and working, using the same methods to poll the HDD, it should be possible to add a DVD drive, and maybe keep the hdd. If the GDROM is on a Bus that has similar features as native IDE like multi ports on one Bus... Then there shouldnt be anything from stopping this.

It would be Really cool to have a AIO Board that Has what my project is working on + IDE port with Dual Device support. Maybe have the serial link up to the board with all the main features. Ill start more searching.

 

IIRC, the bus is very IDE like (the ide mod has little parts) and the gdrom can be connected at the same time as its "slave". The bios also shares the same bus iirc.

I was already looking into making a board that replaces the gdrom and has the extra bios and IDE port on it, you could then screw a 2.5 inch ide drive to the pcb - all in the gdrom space.

 

That board would have an extra bios? How can it replace the bios from the g1 bus? Or it has other connections? Anyways that's a nice project!

FG

[EDIT] And yeah it's almost plain IDE, plus added SEGA SPI interface commands that are now kinda well known. DS can already access the GD-ROM drive and hdd at the same time, e.g. to dump a GD-Rom to hdd.

 

Ok so doing some digging, The Super H SH4 in the DC has a native PCI Interface, with the instruction set for it.

EDIT: NVM its the 7751 that has pci not the 7750 on the DC... But the DC SH4 has PCMCIA which might be the G2 Port

 

im very interested in this set up... but no matter where it goes... we also have to worry about Costs... good luck and hope to see progress...

 

Bad_Ad84: "I was already looking into making a board that replaces the gdrom and has the extra bios and IDE port on it, you could then screw a 2.5 inch ide drive to the pcb - all in the gdrom space."

something like we can see from DS + IDE(HDD), or gdrom emulator w/ hdd and bios?

 

http://www.cyrusdevxcloud.tk/public.php?service=files&t=3445efacdb9d05a11cbc0bbdd5e6cac6

Just a quick schematic, not even sure if its functional the way it is in the pdf. Was my first time using Eagle... Always would use paper and pencil...

Sv3 port is the DC-Serial In:
Sv1 SPI port (missing one trace XD):
Sv2 ICSP Header for PIC:
Sv4 GPIO:

X2 SDCard Port:

The six little points up top, are jumpers, first 2 on the left - enable ICSP and USB powering of the board, Only when not connected via DC. The last 4 Are for SPI Config settings.

 

This is not usable idea, you can't really improve situation, even if by some miracle a little speed up the interface. Because the main problem is not in a speed.
The main problem is PIO mode... CPU lost much time. Games oriented to async DMA data transfer, the main is ASYNC. So any PIO mode - will lag in games.
Even on the HDD in PIO (~25 Mbit/s!!!) - many games will lag. Event on the HDD in DMA but in sync mode (90 Mbit/s!!!!!!) - some games will lag.
So only async DMA can be make the games fully happy.

DC Serial can work with DMA in original UART mode, but really usable speed without errors is max 1.5 Mbit/s... it's too slow... It's not a max theoretical speed, it's can be up to 3-5 Mbit/s, but it's not works in general because have much errors at transfer.
Current soft SPI can give up to 6 Mbit/s.

 

Hey SWAT , yeah im going to ditch the SDcard interface part of it. Just going for a GPIO Control Module now. Im not 100% sure if what u said also goes for the gpio part of the idea. hopefully not.