Chris Johnson Posted May 23, 2006 Report Share Posted May 23, 2006 I'm trying to build something a bit like http://monome.org/ from scratch (i.e. not using the MIOS system). I'm looking at the 18F4550, but am rather worried by the problems with the chip that stopped the USB PIC module development.I have a question regarding the bug. It appears to be in the EUSART section of the PIC. Does this cause any problems with the USB functionality of the chip, or was it just the MIDI serial side of the USB <-> Serial bridge that had the problem?For my project I'd like to use the CDC firmware for the USB interface, and just connect some buttons and LEDs to other ports of the PIC, without using any serial connections to the PIC (other than the USB). Am I right in thinking that I should not encouter the bug?One further thing - has anyone tried burning an 18F4550 chip with the JDM programmer? I have a JDM already and would ideally like to avoid making another programmer if I can get the JDM to work on the 18F4550.A appreciate this isn't really to do with the MIOS project, but this site is just about the only place where the silicon bug in the 18F4550 is documented at all...Many thanks, Quote Link to comment Share on other sites More sharing options...
TK. Posted May 23, 2006 Report Share Posted May 23, 2006 Hi Chris,to say it short: for such a project you won't run into problems. In the meantime I've programmed a completely assembly based USB firmware in order to get rid of the C18 compiler. As workaround for the EUSART bug I'm using the MBHP_IIC_MIDI module. Resp. I'm using 4 of them in order to get 4 MIDI IOs. The USB peripheral works ok, but I noticed a strange effect for which I don't have an explanation. I can only say, that it happens with the CDC example as well as with my own firmware: if the OUT pipe is not serviced immediately, and something should be sent through the IN pipe, the IN pipe can be blocked for more than 40 mS. I've described the details here: http://www.midibox.org/forum/index.php?topic=6413.0, but unfortunately only in german (babelfish.altavista.com helps to translate the text)However, so long you don't use the chip as a bridge, and USB streams are handled internally, you will propably never notice this issue. Even with my project (MIDI bridge) the problem can only happen under very special circumstances, which might be acceptable.I never tried to program the PIC18F4550 with a JDM programmer...Best Regards, Thorsten. Quote Link to comment Share on other sites More sharing options...
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