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Forum: ARM programming with GCC/GNU tools Olimex power supply


von Abe A. (olimex)


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Hi,
I'm new here, so maybe this question was already asked.

I'm using Olimex-board LPC-P2138 and programming it with Rowley Cross
studio 1.9.
I disconnected ARM-USB-OCD connector and tried to use an external power
supply (i just disconnected power supply, not JTAG) but cross studio
doesn't recognise the target. Even when i download program to target and
then connect an external power supply, program doesn't work. Where can
be the problem?How to use an external power supply?

Thanks for answers!

von Martin T. (mthomas) (Moderator)


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Abe Abe wrote:
> Hi,
> I'm new here, so maybe this question was already asked.
>
> I'm using Olimex-board LPC-P2138 and programming it with Rowley Cross
> studio 1.9.
> I disconnected ARM-USB-OCD connector and tried to use an external power
> supply (i just disconnected power supply, not JTAG) but cross studio
> doesn't recognise the target. Even when i download program to target and
> then connect an external power supply, program doesn't work. Where can
> be the problem?How to use an external power supply?

I do not own this board and do not own the Olimex ARM-USB-OCD so take it
for what it's worth: Did everything work as expeced while you have used
the power-supply from the ARM-USB-OCD connected to the board's
power-jack? Than you unplugged the power-supply from the USB-OCD and
connected another power-supply? Did you connect the other supply to the
power-jack or did you use a 3,3V supply and connected it "behind" the
regulator (VR1)? If yes, is the external supply stable?

Some tests: disconnect the JTAG-device, connect you external
power-supply and measure the voltage (i.e. at Pins 2 and 4 of the
JTAG-connector, see schematic). Verify that the voltage is around 3.3V.
Compare this with voltage measured when the ARM-USB-OCD is used as
power-source. Check if there is a common GND.

If Cross-Studio detects the target later even with the external supply
but the firmware does not run after power-toogle check if the firmware
gets loaded into the controller's flash-memory (not just in RAM).

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