Documentation about the 160/180 SPI Bus ?

[demik]

Hello,

I knew for a long time that this series of the powerbook has a SPI bus on the modem connector. From the developer notes it's mentioned that the SPI host is likely the Misc GLU:

The Miscellaneous GLU is a modified version of the Miscellaneous GLU used in the PowerBook 140/145/170. This chip also supports the new SPI modem interface

The documentation (Modem Electrical Interface section) also describes how to switch the modem slot from RS-232 to SPI. But what about the MacOS side ? Later in the note there is note that Apple will release specifications and software tools for SPI modems when they become available.

Does someone know if such documentation was even released ?

 

[Phipli]

If I remember, there was some documentation on the SPI (or was it I2C??) in the S-Video port on the 8100? Perhaps it was the 840av, but it was fairly light. @Arbee - do you happen to have anything applicable hidden in a drawer?

 

[Phipli]

Anything in these? (I'm away from my Mac sorry)

 

[demik]

Thank you for this. I read a few of the files but no motion of SPI.

the first file is similar to what you can read in "designing cards and drivers for the macintosh family third edition"

I'm assuming the Express Modem is the one using it. On the Express modem dev kit, everything point to using the communication toolbox for that, which makes sense, but that also means no native SPI outside of that.

Fun stuff, one of the feature of the 1.2 firmware was increasing a few buffers so you could pay for pr0n:

It allows the dial string to include a credit card number for specific uses.

 

[luRaichu]

Would an internal SPI modem be faster than serial or DaynaPORT?

 

[Phipli]

Would an internal SPI modem be faster than serial or DaynaPORT?

No, modem speeds were limited by the speed over the phone line, not the serial port. Ignoring CPU overhead.

 

[croissantking]

What are the practical benefits of using the SPI interface?

 

[luRaichu]

No, modem speeds were limited by the speed over the phone line, not the serial port. Ignoring CPU overhead.

what if it was Ethernet or Wi-Fi instead of POTS. If you know what I mean.

 

[Phipli]

What are the practical benefits of using the SPI interface?

I don't think it is a benefit type senario - SPI is more of an inter-component protocol, and so handy for talking directly to a lot of chips directly in their native tongue so to speak. For example, if SPI is working on this port, you could add a port expander to do GPIO, or DAC chip or a sensor or whatever.

On the other hand, Mac serial can use long cables.

what if it was Ethernet or Wi-Fi instead of POTS.

SPI doesn't have a fixed speed, so it depends what speed it was run at. The RS422 serial is no where near fast enough to get good ethernet speeds though, so you'd do better to look to the SCSI port.

 

[croissantking]

I don't think it is a benefit type senario - SPI is more of an inter-componemt protocol, and so handy for talking directly to a lot of chips directly in their native tongue so to speak. For example, if SPI is working on this port, you could add a port expander to do GPIO, or DAC chip or a sensor or whatever.

On the other hand, Mac serial can use long cables.

Interesting. @demik what are you looking to do?

 

[Phipli]

Oh, yeah, SD cards can also speak SPI (slowly) if I remember correctly. But that just gives you the connection, you'd still have to write all the drivers to talk to it and mount it on the desktop etc etc.

Also, sorry @demik for rambling on your thread.

 

[luRaichu]

I think you'd have to sign an NDA in order to get access to the full-speed SD interface. So, many homebrew devices just use SPI last I checked.

 

[halkyardo]

I'm very interested in this too; if the SPI clock was fast enough, it could potentially be an option for building an internal ethernet adapter for the 180. But on the other hand, I'm rather hesitant to open mine up to experiment with such a thing...

 

[demik]

@Phipli No worries I 100% agree with what you said.

@croissantking just R&D, sorting stuff from the TODO list . I kinda want to use another MCU in SPI slave mode and communicate with it from within MacOS. Hardware side is doable, software side we do not have any idea where to start.

However, do remember that anything over SPI would be somewhat slow and will eat way more CPU or bus time than anything parallel. The Misc GLU is 8 bit wide already, so clocking that into serial (assuming the same SPI clock, which will probably be slower) would be again at least 8 times slower. So for a SE/Ethernet style, we are talking at least 16x slower

Some 68030 systems such as the T030 are using such a setup (using a TP3465 Parallel to SPI glue chip), and the speed is not much better than LocalTalk. As @Phipli said, SCSI is a better way to do Ethernet on theses.

@halkyardo yeah this is probably very destructive, we need spare CPU modules for that (and maybe @croissantking schematics )

 

[eharmon]

Oh, yeah, SD cards can also speak SPI (slowly) if I remember correctly. But that just gives you the connection, you'd still have to write all the drivers to talk to it and mount it on the desktop etc etc.

Also, sorry @demik for rambling on your thread.

It's not so slow, a PS2 driver was written to use it's memory card slot SPI to speak directly to SD cards: https://www.psx-place.com/threads/m...d-sd-driver-for-the-ps2-sio2-interface.29210/

Does > 5MB/s which isn't bad at all, all things considered.

 

[Phipli]

It's not so slow, a PS2 driver was written to use it's memory card slot SPI to speak directly to SD cards: https://www.psx-place.com/threads/m...d-sd-driver-for-the-ps2-sio2-interface.29210/

Does > 5MB/s which isn't bad at all, all things considered.

OK, yes, but isn't the card's advertised speed by a long way. Plus the PowerBook is unlikely to support 5MB SPI.