Hardware I2C

[Toley00]

Is it possible to use the Hardware I2C in PicBasic Pro?

I need to read faster than I2CREAD PicBasic Pro command. Even with a 20MHz crystal I'm unable to obtain full speed I2C.

Surely someone have ever work on that issue. Maybe an assembly include?

Thank you

[BobK]

Hi Toley00,

It may be worth your time to download the I2C Bus Specification manual from Phillips. There are 3 data modes for I2C, Standard Mode = upto 100kbits/sec, Fast Mode = upto 400kbits/sec, and High Speed Mode = 3.4Mbits/sec. I've only used I2C for RTC's using both software I2C and Hardware I2C. I didn't have to set anything up special on my PICs for speed. But you do have to put a 10ms pause after any write command to give it time to catch up or settle down. I have seen some posts on this forum where I2C worked better when it was slowed down.

Don't know if this helps, but I think maybe their manual might give you a better insight into the whole process.

BobK

[Toley00]

Thank you BobK for your reply.
I already know about I2C timing protocol, and I use it in many project already. I just need it to read an EEPROM faster than I2CREAD can do.
Thanks for your help but a 10ms pause will not give me speed...

[SteveB]

I don't know what PIC you are using, so I can't promise anything, but I've attached a file containing some portions of code I have used with the hardware I2C on a PIC 18F4620.

The file is a compilation of cut and past from a few include files, and has only been minimally "cleaned up" for public viewing. It has 4 sections:
1) Basic PIC and HSEROUT setup (mostly to reinforce what pic and how it's configured)
2) The meat of the I2C commands
3) Samples of Large Block Reading/Writing to an EEPROM
4) Samples of Reading/Writing to an RTC

Hopefully this will get you started.
Best of luck,
Steve B

Disclaimer: Looking a little closer I recall this being one of my first PBP-ASM items I tackled. It worked, and with other things pressing, I haven't gone back and cleaned things up, like unused variables (DelayCtr1 and DelayCtr2) and rements of HSEROUT commands used to debug.

[Toley00]

Thank you SteveB, looks like what I need. I will take a closer look and adapt it to my needs. I'm using a PIC16F886, but I think all MSSP modules work the same way, and I only need to read from the EEPROM.

[SteveB]

Thank you SteveB, looks like what I need. I will take a closer look and adapt it to my needs. I'm using a PIC16F886, but I think all MSSP modules work the same way, and I only need to read from the EEPROM.

A couple of things right off the top of my head. The buffer size will need to be reduced for a 16F. Also, the way I allocated variables to "BANKA" or "BANKX" in the declaration statements will also need changing. If I get a chance later I'll try to give it a look-over for anything else. As I recall, I think I got the basics of the ASM routines from a Microchip document/source, and adapted them for the 18F. So that might also be an avenue to persue.

Steve B

[J. Mark Wolf]

Also consider the RAMTRON FM24C256 32K X 8 eeprom.

It reads and writes at FULL I2C buss speed. No artificial delays required.

It is also pin-for-pin compatible with many common serial eeproms, and might just plug directly into your eeprom socket.