SIMtrace prototype bug report

Hi all, I've done a lot of work on the SIMtrace prototype over the last couple of days. A number of bugs were easy to re-work, or are at least known and can be improved in the second revision. 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). I think there is little that can be done, except: a) finding a better alternative analog / bus switch component this might be an option for the second prototype, but is not easy to fix in the existing board. I'd love to see something that has milli-ohms internal resistance, not ohms. Advantage: Also removes the couple-of-ohms from the IO,RST,CLK b) permanently connecting VCC_PHONE with VCC_SIM this sort-of violates our idea of splitting the SIM card and the phone side for MITM. c) always supplying VCC_SIM by the SIMTRACE board, ignoring VCC_PHONE This would make a lot of sense, if we'd also provide VCC_PHONE to an IRQ-capable GPIO of the SAM7. We could then detect VCC_PHONE changes in software and switch the VCC_SIM from the IRQ handler. This introduces some delay, but I doubt that it is more than what would happen in case there was some uF-range capacitor for VCC stabilization in the hardware. I will try solution 'c' as a work-around, it simply means cutting one trace and adding one wire. -- - Harald Welte <laforge(a)gnumonks.org> http://laforge.gnumonks.org/ ============================================================================ "Privacy in residential applications is a desirable marketing option." (ETSI EN 300 175-7 Ch. A6)