[WP-34S] Cable and flashing options for Mac users
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01-22-2015, 10:43 PM
Post: #63
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RE: [WP-34S] Cable and flashing options for Mac users
(01-22-2015 06:59 PM)John Galt Wrote: I completely agree with you that there is something electrically wrong (...) Hi again, John, Great effort and nice project of yours. If I understood your test results: - The USB-to-TTL-Serial cable works fine, as tested in loopback mode; - The software tool to upload the firmware looks fine as well; - The calculator can power ON, confirmed by an increase in current consumption. Here is what I believe it is happening, and you sad it all: - It is normal to see some signal cross-talking on the scope when you remove the cable from the calculator: This is caused by capacitive coupling on the cable and a high impedance on the Rx input circuit; - The RX line must be loaded by the calculator output driver circuits, imposing a low impedance on the connection. - So, as you say, it doesn't matter whether the cable is connected or not to the calculator - the result is the same. And why? Most probable cause: The RX connector pin is not making contact with the calculator PCB pad, even if it seems to be making contact. I would check it it a continuity meter. Please share your results with us - Great job! Jose Mesquita RadioMuseum.org member |
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