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Harald Welte laforge at gnumonks.orgHi Sylvain, On Sun, Jun 19, 2011 at 06:54:35PM +0200, Sylvain Munaut wrote: > >> > However, I think there's one pretty serious problem in the hardware > >> > design: The bus switch has something like at least 5 (rather 16Ohms) of > >> > internal 'on' resistance between the sim card and the phone. While this > >> > _might_ still work for I/O, nRST and CLK lines, it definitely doesn't > >> > fly for the supply voltage (VCC). > > Why not just keep the bus switch IC for the signals. ( ~ 20 ohms won't > be a problem for sure ). well, if you're sure the ~20 ohms is not a problem, then I think we can indeed stop searching for a proper switch. The big question is though: Why does it not work yet? The nRST, CLK and I/O are still routed via the switch. The switch is in the correct position, as I can apply 3.3V with a 10kOhm resistor to any of the three lines on the 'phone' side, and I can see the corresponding signal changing on the SIM card side. However, the high-voltage is only about 2.5V on the SIM card side. Vcc is supplied permanently from the SAM7 to the SIM card socket. Still, no communication between phone (or smart card reader that I use instead of a phone) and the SIM card is possible at this time. Hopefully Kevin has some ideas tomorrow (he'll be visiting me to help debugging). Regards, Harald -- - Harald Welte <laforge at gnumonks.org> http://laforge.gnumonks.org/ ============================================================================ "Privacy in residential applications is a desirable marketing option." (ETSI EN 300 175-7 Ch. A6)