From: dsharp@SoftHome.net - 2005-12-14 21:24:57
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Thanks for the suggestions. I'll have to put off some of the tests until tonight, but I was able to short together the TX and RX pins on the gumstix (TTL)-side of the level shifter and when I typed on the keyboard, the characters I typed were echoed back to my console. So the cable's good, and (one way or another) it's gotta be really close to working... > First of all, when you're using the breakout-gs, you have the tweener > removed right? Correct, only one was tested at a time. > 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). Here's my setup, correct me if I'm missing what you're suggesting. The RX line from the Gumstix goes directly to the corresponding pin on the level shifter (and from the test conducted earlier, we know those pins are all correct on the level shifter, etc). Then, in addition, there is a 10k resistor going from that RX pin to (3.3v) VCC. You're suggesting to leave all of that intact except to disconnect the level shifter's "gumstix-rx" pin from the resistor and the gumstix. This would help determine if, say, the level shifter were somehow messing things up (say by pulling the line low for some crazy reason, for example). Given that the level-shifter is now known to work (at least using the "paperclip" test above), it seems unlikely to me that that's what's wrong. I will perform this test though, tonight. > At this stage I would connect FORCEON and FORCEOFF to Vcc. I currently have /FORCEOFF tied to Vcc and FORCEON tied to.. WAIT... Hmmm.... Ok, now that I look at it, it appears as though I accidentally connected FORCEON to 5v (instead of the 3v I'd been using for the rest of the Max). Seems odd that it would work with the PC but not the Gumstix, I'm a little skeptical that this is the problem (though it needs to be fixed, of course). Regardless, I'll have to get back about whether this changes anything or not in order to be thorough. I'll get back tonight about this stuff, and hopefully it'll all magically go away. ;) Thanks for the help guys, -Dave |