From: Dave H. <dhy...@gm...> - 2005-12-14 19:24:45
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Hi Dave, On 12/14/05, ds...@so... <ds...@so...> wrote: > I've been having some trouble getting my serial port to work. Here's the > setup: gumstix board -> breakout-gs -> MAX3233E (3.3v dual RS232 > transceiver w/ internal caps... seems like a decent enough level-shifter > to me for the job) -> homemade null-modem cable. I know the software end > is setup correctly because I can swap the breakout-gs for a tweener (and > use the stock null-modem cable) and it works like a champ. To my knowledg= e > the homemade cable is correct... The connecting pins 3 & 4 was referring to the connector on the robostix that's labelled "gumstix". In the case of the gumstix-rs the pin numbers happen to match up with the robostix. First of all, when you're using the breakout-gs, you have the tweener removed right? If you don't then you'll have the MAX232 on the tweener and the one on your board both trying to the drive the RX line, which may cause what you're seeing. I'd try this. Allow the TX line to go through your MAX232. Leave the RX line disconnected. Put the 10K resistor between RX and Vcc (pins 3 & 4). If booting up still drops you into uboot then you've got some kind of problem with your breakout-gs board. You should be able to plug the tweener and the breakout-gs together (no gumstix) and check for connectivity between your FFUART Rx line and the Rx line on the hirose connector. If you look at this page: http://www.gumstix.org/tikiwiki/tiki-index.php?page=3DTweener-Mod the trace which would be cut by one of the red lines is the Rx line to the gumstix. So what you want to do is locate where the via between the two red marks comes out on the other side of the tweener. Check for connectivity between that line and the FFUART-Rx line with the breakout-gs and tweener plugged together (this assumes that you didn't cut that trace). If you have good connectivity, then the problem is probably the connection on the MAX232 side of things. At this stage I would connect FORCEON and FORCEOFF to Vcc. Also, just to verify, R1IN or R2IN goes to the PC and the corresponding R1/R2OUT goes to the breakout-gs. I'm assuming that the Tx stuff is right since you said you can see the boot message (at least into uboot). -- Dave Hylands Vancouver, BC, Canada http://www.DaveHylands.com/ |