abardsley :
The JTAG lines to the STM32 are sourced from the ST7. I wonder how hard it would be to reprogram the ST7 to allow more direct access. The programming lines for the ST7 are available on the circle and ST give app. notes for parallel port programming via that interface. Hmm.
They are. But the lines may very well be tristated (high impedance) when the ST7 isn't active (no USB cable plugged in, for instance). Unfortunately, I do not have the equipment to test that out. If that cannot be assured, then surely holding the chip in reset (by tying pins 1 and 5 of J3 together, for instance) would do it. Once they are assured to always be tristated, then not only would it be possible to flylead a JTAG interface, but Serial Wire Debug would become available as well. Of course, one could just desolder the chip, entirely. Either way, it looks like all of the JTAG lines (the usual 4 plus TRST and SRST) are available on vias under the chip.
I looked into reprogramming the ST7, but that poses the same problems that the Windows-only support for the RLink programmer does. The only compiler I've found for ST7 comes from Raisonance, and is Windows-only. The ST7 core appears to be some variant of 6502, but the status register is laid out quite differently, and I don't fancy trying to hack an existing 6502 C compiler to deal with it. Besides, that is unlikely (though conceivably possible) to be the only difference. I haven't touched 6502 since High School.
Last edited by lou (2008-05-13 12:55:13)
