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Kevin Redon kevredon at mail.tsaitgaist.infoThanks for the fast analysis > > 2) It might be an idea to use a 2.5mm jack (like Compal phones) for the > DBGU, instead of the FTDI-6pin-header. I guess more people in and > around the Osmocom projects have a T191 cable than a FT232 cable with > the 6-pin header. What do the others think? I would choose jack 2.5 only, but I will put both. > > 3) It might be nice to have an ADC input connected to the VCC_OUT line, > to be able to measure the SIM card supply voltage as it is output > by the phone. ADCREF of course would have to be connected, too. I will add it. > > 4) It is generally good 'style' to connect the nWP to some I/O line of > the CPU (together with a pull-down). ack > 5) I think the IN/OUT naming is a bit misleading. E.g. "VCC_OUT" is the > source of the VCC power, i.e. the phone. It may be better to call > the signals leading to the phone {VPP,I/O,CLK,RST,VCC}_PHONE and the > signals leading to the sim {VPP,I/O,CLK,RST,VCC}_SIM ack > > 6) The USB pull-up mechanism is missing. This is required for properly > signalling a USB bus reset to the host controller. Please refer to > the OpenPCD schematics for an example circuit. It just requires one > transistor and some resistors. It has also proven useful to connect > the nRESET to that pull-up circuit to make sure a cpu-reset leads to > a bus reset as well. > > 7) A 5.6V Zener diode makes sense as over-voltage protection at the USB > 5V power supply line I will have a look for it > > 8) The two 47uF capacitors at the 3.3V line and the 22uF capacitor at > the 5V line might be above the USB specifications for capacitive > load. See Section 7.2.4.1 of the USB spec, where I believe it says > you can only put a cumulative capacitance of 10uF at the downstream > end of a Vbus. We might ignore that, or use something like a > LM3525 (or even a TI TPS2151 which is a LDO with built-in in-rush > current limiter). OpenPCD1 v0.4 is not being sold anymore exactly > due to this problem. didn't know than, I will change the ld1117 with a tps73633 (less expensive then TPS2151, and fits perfectly). I don't understand why the capacitor at the 3.3v line affect USB, but I will minimize it. > > 9) I would only use a jumper for the TEST singal, as we probably only > need it very rarely during sam7dfu testing/porting. After that, we > will use USB DFU for updates ack > > 10) However, it is useful to have a push-button for DFU-mode activation, > this is a simple switch between Vcc and a GPIO. Normally, DFU is > activated over USB itself. However, if the firmware is dead, this > BOOTLOADER switch can help with recovery (once again, see OpenPCD) I will take the openPCD design > > Regards, > Harald WiP, Kevin