Connecting I2C to PBI

[evilmoo]

I realize there are probably multiple right answers on how to do this, but...

 

I was considering how to add an I2C bus to an Atari. I saw Guus Assmann's project to run it via a joystick port, but it would be much faster if it could be interrupt driven and the bit-shifting could be offloaded, and it was connected via PBI. I found this other 6502 project (http://6502.org/users/andre/csa/scsi/index.html) where a PCF8584 was used. Is there a better chip for doing this, or is this the most appropriate?

 

Thanks for any input/help.

 

[Marius]

I2c is serial ... why need PBI?

 

I connected an rtc to pia. Through joystick port does not work so well due to fact that there is a component (a coil or a capacitor can not remember) making trouble.

Edited December 4, 2016 by ProWizard

[ricortes]

OK, I know you said I2C. Is there a specific device you were looking to implement with I2C or were you just looking for a fast serial interface? I *THOUGHT* uSD cards supported SPI and there is a much less rigorous implementation.

 

http://sbc.rictor.org/65spi.html

 

There's a lot of stuff that supports SDI IIRC. Everything from the uSD to WiFi and Ethernet.

[+David_P]

There are insanely cheap Arduino pro mini clones out there; you could use one on the SIO bus to do your I2C work.

[+mytek]

Most all of the Microchip PICs have hardware I2C and SPI support built-in. It would be a relatively easy matter to use one of these on any available I/O from an A8 (PBI, JOY, or SIO), and then use the PIC's internal RAM as a data buffer. It would of course require custom firmware to be written, but since we already have PIC programming capability via JOY2PIC it would be an inexpensive DIY project for distribution. Just something to think about. And also most PIC's have an internal UART as well, so SIO interface would be a snap.

 

- Michael

[Rybags]

A buffered system, automated would be a good way. Cartridge, have the buffer and control registers accessable in the $D5 page.

[+David_P]

The challenge with the Cart port is that there are too many other items wanting to use it nowdays - USB, Ethernet, mass storage...

[evilmoo]

I2c is serial ... why need PBI?

 

I want to be able to use the PBI boot ROM area for drivers and SIO emulation.

[evilmoo]

OK, I know you said I2C. Is there a specific device you were looking to implement with I2C or were you just looking for a fast serial interface?

 

I2C seems to have the most diverse base of available devices, but perhaps I'll look at the 65SPI too, or produce a similar 65I2C chip. Thanks for the link.

[evilmoo]

Most all of the Microchip PICs have hardware I2C and SPI support built-in. It would be a relatively easy matter to use one of these on any available I/O from an A8 (PBI, JOY, or SIO), and then use the PIC's internal RAM as a data buffer. It would of course require custom firmware to be written, but since we already have PIC programming capability via JOY2PIC it would be an inexpensive DIY project for distribution. Just something to think about. And also most PIC's have an internal UART as well, so SIO interface would be a snap.

 

Is there a particular PIC you would recommend? Or one you've seen used in other projects?

[ricortes]

Well, you could still do I2C and get SPI fairly simply. http://www.nxp.com/documents/data_sheet/SC18IS602B.pdf Anyway, that is why I asked if you had a specific function/device you wanted to hook up. If you want to create a uSD mass storage on the PBI, IMHO SDI is the way to go. If you want a specific device for things like robotics, I2C is fine too.

Edited December 5, 2016 by ricortes

[+mytek]

 

Is there a particular PIC you would recommend? Or one you've seen used in other projects?

 

Check out this link to JOY2PIC software and you'll see a listing of some of the chips I use: https://github.com/dmsc/atari-picprog/releases/

 

Quite a few of the 8-Bit series PIC's will have I2C capabilities built-in. So a lot of it comes down to what you really want to do, what other peripheral support is needed, RAM required, and Flash program space it'll take for your code to run in. You can always go straight to the source: http://www.microchip.com/design-centers/8-bit and look at what they have to offer in a parametric form (click on a particular MCU family and drill down to get a table showing what's inside).

 

- Michael

Edited December 5, 2016 by mytekcontrols

[Mathy]

Hello guys

 

The SCART plug also has I2C on board. TVs and VCRs use it to tell each other which channels are used in what order. As in: "Broadcaster 1" is behind button #1, "Broadcaster 2" is behind button #2, etc. Not sure what else we could do with more modern devices like set top boxes etc. but it would be nice to have a look inside... :-)

 

Sincerely

 

Mathy