What is the difference between JTAG-USB-TINY-H and JTAG-USB-OCD-H

[franchan]

I understand about
- there's a price difference,
- the handy 5V power supply on the OCD
- an even lower voltage range for the OCD

But what are technical merrits of one over the other when doing the actual debugging?

What's the use of the serial port on the OCD?

(Recent PC/notebooks don't have any (external) serial port anymore.
Is my understanding correct that one connects over USB with the PC,
this offers a virtual RS232 on the PC.
When using this virtual port, it triggers this RS232 on the dongle?
So you can hook up a serial debug output from your board to this RS232 on the dongle,
and get the results on the PC?
That seems handy for nowadays notebooks and PC ...
On the other hand some low-cost development boards have just TTL/CMOS level output.
That's not enough for connecting to the dongle's RS232 level signal (that's even destructive).
Maybe that's a nice feature to add in a JTAG-USB-OCD-H version-2 from Olimex :-)

Thanks for any clarifications

[JohnS]

I don't see why you mention RS232 and serial ports.  These devices plug into USB and are used through USB (such as via OpenOCD).

You can use RS232 for debug purposes if you wish but JTAG is at a different (mostly non-invasive) level.

Pick the one whose features you like/need.

John

[LubOlimex]

Hey,

The hardware difference between TINY JTAGs and OCD JTAGs is mainly that the first lack protection buffers – the devices tend to fail faster when used for manufacturing volumes of work (e.g. you flash 500 devices a day with them) ; and the lack of virtual COM/RS232 port. The COM port at the debugger is handy and saves spaces in case your computer needs a COM port (but doesn't have such on the motherboard) - this tool can be used as a computer USB to COM port.

OCD-H can also be powered externally if you provide voltage to the PWR JACK. OCD-H is also suitable for programming devices at lower voltages - down to 1.65V (compared to the 2.0V of TINY).

Best regards,
Lub/OLIMEX

[franchan]

Thank you! Meanwhile I received the ocd jtag! Works OK, I still have debugging and flashing questions but post that in a separate thread.

I use the pwr jack to power the stm32 board. Did not realise I could power the jtag itself through this plug. I see USB power does the trick and I'm happy with that approach.

This COM port expects RS232 levels I guess, not TTL levels?

[LubOlimex]

Hello franchan,

Glad the debugger works.

The signal levels expected are in -5V to +5V range. The signal should not be in the -3V to 3V range, or else it won't be valid.

Best regards,
Lub/OLIMEX