LK404-25, I2C and dropped characters

mlind · Post by **mlind** » Tue Oct 03, 2006 9:59 am

Ok, I'm currently lost. I can get the LK404-25 to display text fully if I step through the code (TI TMS320F2808 chip for those interested), but if I take the breakpoints out and let it run, 1/2 or so of the characters don't get displayed (varies depending on which way I was sending the characters to the screen -- I've tried a bunch of ways to get around this). If I throw in a couple delay/timing loops, it seems to display all text, though that's kind of like flying blind & hoping the characters get displayed (what happens if there is a full moon AND the new guy's name is Harold? I don't want to be debugging display issues in the back 40 of nowhere if I can avoid it). The last rev/rewrite of the display code from last night works best, but I don't seem to get any NAKs and the 2808's transmit buffer empties like there was no problem... Is there any register I can check on the display, or command I can send to get some sort of flow control going?

Martin.

Raquel · Post by **Raquel** » Tue Oct 03, 2006 11:00 am

Hello mlind,

Thank you for your post.

Can you please tell me the serial number on the back of your LK404-25?

Unfortunately, there are no registers to check on the display. The NAK/ACK bit is the flow control on I2C. I have a feeling that you were communicating with the module a little too fast, and that the delays that you have inserted has slowed the transactions down which resulted to a better responding display.

Best Regards,

mlind · Post by **mlind** » Tue Oct 03, 2006 11:20 am

S/N: 6M09-2024

That's my feeling too, since stepping through (delay implicit) worked, but going full speed didn't. Checked the clock lines and they're going @ 385kHz, which should be in spec for 400kHz i2c.

If I go into a loop on the receipt of a NAK, and continually send the last character, will the display NAK until its ready and then ACK? In the end, I want to minimize the time in the display routine(s) and not have to insert delays here & there -- its a bit of a kludge imho. I'll look into the NAK thing a bit deeper tonight & see if something falls out of the tree...

I kinda wish the I2C end of things was a bit more documented, though... :-/

Martin.

Raquel · Post by **Raquel** » Tue Oct 03, 2006 12:05 pm

Hello mlind,

Based on your serial number, I can guess that your LK404-25 has firmware version 5.1 and the crystal on the board is 8MHz. Can you please confirm? You do not need to read the version number, just tell me about the crystal.

Thanks,

mlind · Post by **mlind** » Tue Oct 03, 2006 12:11 pm

8.00C56, metal can, through-hole.

Not much more (that is useful) can be said...

Martin.

Raquel · Post by **Raquel** » Tue Oct 03, 2006 2:07 pm

Replied via email.
Thanks,