> Dave- you responded to my question about uisp and robostix... Am I missi=
> something? How come you need a programmer when using the Desktop but don=
> need one when using the gumstix? Isn't the gumstix connection to the rob=
> just straight serial (for programming)?
No. The robostix is programmed using SPI. On the other AVR's, they
using MISO and MOSI for this. For some unfathomable reason, they chose
to create a couple of new pins called PDI and PDO for this purpose,
and they share the RxD/TxD pins.
The complete set of signals required for programming via ISP (In
System Programming) is RESET, SCK, PDI and PDO.
Since we didn't want to tie up the UART on the robostix, but felt that
some people might want to be able to connect the robostix to the
gumstix via serial, we arranged for the STUART port to be right next
to the UART-0. This is why the jumpers are needed.
The robostix_drv.ko modules emulates enough of a PC parallel port to
connect some of the parallel port pins through to some GPIO lines on
the gumstix, which are connected to the RESET, SCK, PDI and PDO pins.
You can download a bootloader to the robostix, using ISP based
programming. The bootloader can then use any communications method it
has available to program the remainder of the flash.
I commonly use serial based bootloaders on my bots. For the robostix,
we had an i2c connection, so that's why I wrote the i2c bootloader.
> I guess I'm confused why one actually needs a "programmer" rather than ju=
> some software and a serial connection.
Because if the flash on the robostix is empty, you CAN'T program it
using serial, you need to use the SPI technique.
The "programmer" connected to the host can be super simple, as simple
as 4 resistors connected to the parallel port:
By adding the two jumpers, this is essentially what you get going from
the gumstix to the robostix.
> PS I ask as more for my own curiousity rather than trying to avoid buying=
> programmer (and the hassle of ordering one).
Building one can be quite simple too.
Vancouver, BC, Canada