Olimex ARM-USB-OCD-H output voltage

Started by lim, October 12, 2020, 05:24:55 am

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I tried to use the output voltage to power up the Olimex STM32-E407 board. Having tried many times, and two different A-B USB cables, but no avails. The measured voltage for the Jack output is always below 0.5V. However, the LED is in Red colour.

The manual says it is fixed to 5V and draw the voltage from a USB port. I have also tested the USB port and managed to power a high-power LED. Of course, I have confirmed that the board is working connecting to a USB-Jack.

Further test when connecting to a PC USB port, the LED of ARM-USB-OCD-H turned Green upon plugged in, but gradually turned to RED, and the STM32-E407 was switching Off.

I have also tested on the second unit. Both behave exactly the same.

Can someone help, please? Why I can't get into Support page of Olimex webpage?

Also, I am puzzled to know that Olimex STM32-E407 input voltage, through Jack is 6V-12V; however, the ARM-USB-OCD-H can supply the only 5V. Does it imply actually Olimex STM32-E407 can take 5V as well? Does anyone have any comments?


October 12, 2020, 09:34:15 am #1 Last Edit: October 12, 2020, 09:38:58 am by LubOlimex
ARM-USB-OCD-H is capable of powering STM32-E407. You can also power the board via the mini USB connectors (USB-OTG1 or USB-OTG2). There are two things to keep in mind:

1) There is big PTH jumper called PWR_SEL that controls the power input source! Make sure it is set according to your power input.

By default PWR_SEL is set to position that requires external power supply attached to the PWR jack! If you wish to power the board from the JTAG, make sure to set the jumper to position 3-4.

2) Are you sure that the software that you use, doesn't keep the board in reset? It is very typical for the board to be kept in reset by the ARM-USB-OCD-H until programming. This is usually controlled by the software.

Try to program the board to see if that goes through.

QuoteAlso, I am puzzled to know that Olimex STM32-E407 input voltage, through Jack is 6V-12V; however, the ARM-USB-OCD-H can supply the only 5V. Does it imply actually Olimex STM32-E407 can take 5V as well? Does anyone have any comments?

No, you need between 6V and 12V at the power jack. It is different circuit around the power jack to ensure the board is fully powered even when a lot of peripherals are attached. Our experience shows that if we use 5V circuit there, a lot of supplies would dip below 5V and in other cases a lot of current would pass through - by requiring between 6V and 12V we ensure that there is less current passing trough and no under voltage is possible.

You can find suitable 12V adapters online just make sure they fit the on-board power jack. It is this one:


We have some affordable 12V adapters here:

Technical support and documentation manager at Olimex


Thanks for the helping hands. However, I wonder why the JTag outputs 0.4V which I measured? this voltage will not able to power-up the STM32-E407 board regardless of the PWR_SEL. Do I need to alter any jumpers/switches in order for it outputs 5V?


Which pins do you measure exactly? Send me a picture of how you measure (attach it to image sharing web-site or cloud storage like google drive and give me the link).
Technical support and documentation manager at Olimex


I am measuring the Jtag's Power-Jack inner (+ve) again Jack outer (-ve).


The JTag has a voltage output port, a female Jack. By plugging in the provide cord, I was measuring the Jack inner terminal against Jack outer terminal.


This is not good. The power jack should measure 5V. Make sure you measure like this:

What bothers me is that two units showed the same behavior, if it was one unit I would consider the chances of a hardware fault, but two units - unlikely, or maybe something damaged them in similar fashion. In this specific case I would assume that it is probably the USB ports or the cables are not good enough. So first make sure to test with another computer and different brand of USB cables, also test different USB ports if the computer has more than one.

But if the ARM-USB-OCD-H unit got damaged somehow, for example if power was provided on pin 19 of the JTAG connector or power was provided on their power jacks - some hardware damge might have occured. Usually anything above 6V-7V applied to the power jack would be dangerous - it will damage Z1 zener (BZV55C6V8 in SOD80C package) and transistor FET2 (IRLML6402 in SOT23 package) and in some extreme cases even fuse F1 (FSM050 in 1206 package),
Technical support and documentation manager at Olimex


I measured those units exactly how you did. To confirm the ports, tried a 4-port hub and a port on PC, are working, I measured those port voltages, they all about 5.16V. FYI, I still use those ports for other applications. See the measurement, I used the same port from my PC.

I had suspected something not right since the beginning, why wouldn't those power-ups the boards. I was disappointed because the one reason I bought it was because of its function as a power supply. https://files.mycloud.com/home.php?brand=webfiles&seuuid=f5d4b02531cf97c2527fcce4caeaea13&name=IMG_1053

Also, upon connecting to USB port, the JTag LED is Green colour and changing to RED about about 2 to 3 seconds later.

See the video https://files.mycloud.com/home.php?brand=webfiles&seuuid=e7fffc43ce88275f93c4151580950923&name=IMG_1056

Are these still working for flashing/debugging?

What options do I have now, in terms of replacing them?


They are likely not going to power up the boards neither via the power jack, nor via the JTAG connector. They should work alright if the target is already powered.

If you believe that you received the units in that condition refer to the warranty and returns policy here:


Basically we send you return merchandise number (so we can track what was returned and who returned it), then you send the units back, we investigate and refund or replace the units. In case we find out that the units were damaged by the customer we charge for repair or replacement. Let me know if you want to return the units in an e-mail at support@olimex.com - make sure to include a link to this forum thread so we can process it faster.
Technical support and documentation manager at Olimex


I can't return it now, because it for my projects. When the project is completed, I can then send it back. Is it an option?


Sure, just make sure to drop an e-mail at support@olimex.com first so we can issue a return merchandise authorization and connect the return with this forum post, else we don't know what came back and from whom.
Technical support and documentation manager at Olimex