PocketBook Basic 2 (PB614) unresponsive, always in FEL/flashing mode

[DoomsdayDog]

Another idea I've had is to dig into the sunxi wiki and learn how to boot over USB, since the A13 chip is detected by sunxi-fel, but I fear I won't have time to try this before my vacation ends.

[kib]

You can easily check if the buttons are working by a multimeter switched to a continuity tester mode (if you connect the probes you hear a buzzer sound). Then you connect the probes to both pins of the button (you should not hear the buzz) and you should hear a buzz when you press the button. There are 4 pins on each button in fact, while two pins are connected.

For connecting to the UART you can buy USB to TTL adapter , but choose one that supports both 5V and 3.3V as the UART on the ebook is 3.3V.

There are also interesting information about reverse engineering the ebook here: https://www.synacktiv.com/en/publica...-reverser.html

[DoomsdayDog]

Originally Posted by kib

Also, there are no signals on the UART port.

From https://linux-sunxi.org/FEL#Serial_output:

While there are a few different ways to trigger FEL mode, they are not always equal. Some do low-level initialization (load Boot0 and Boot1), and some don't.

If you are going to use FEL mode to retrieve device information, you need a to pick a method of entering FEL mode that initializes Boot1.

Boot1 allows you to use UART, otherwise there is no response from the board I believe. It might be worth trying the button combination for entering boot1:

By holding a standard button

This is usually one of the standard tablet buttons, like the VOL+ key or something.

The following seems to work:

Press and hold the suspected or reported FEL key.
Press and hold the power key for about 2 seconds.
Release the power key, and press it at least 3 times immediately.

Boot1 is initialized using this method.

[DoomsdayDog]

Originally Posted by kib

You can easily check if the buttons are working by a multimeter switched to a continuity tester mode (if you connect the probes you hear a buzzer sound). Then you connect the probes to both pins of the button (you should not hear the buzz) and you should hear a buzz when you press the button. There are 4 pins on each button in fact, while two pins are connected.

Hey, thanks for the tips!

I have tested the power, left and right buttons with an improvised continuity tester (3.3V power source, resistor, LED). Confusingly the LED powers on regardless of button state, but there is a very clear increase in brightness when I push a button, so let's assume the method is valid.

The right button (page down on PB614) is stuck as ON, as nhedgehog suspected. Can it be fixed?

[DoomsdayDog]

Originally Posted by kib

For connecting to the UART you can buy USB to TTL adapter , but choose one that supports both 5V and 3.3V as the UART on the ebook is 3.3V.

I have an Arduino and will find something to handle the voltage difference, but I guess I'd have to solder the wires to the PB board?

[nhedgehog]

Originally Posted by DoomsdayDog

The right button (page down on PB614) is stuck as ON, as nhedgehog suspected. Can it be fixed?

That could be possible. From what I see, the directional buttons are soldered hollow metallic caps with rubber glued on top of it. I would carefully try to remove the rubber and either unsolder the metallic cap or try to remove the dent, that I'm sure exists under the rubber, without unsoldering it.

[DoomsdayDog]

Originally Posted by nhedgehog

That could be possible. From what I see, the directional buttons are soldered hollow metallic caps with rubber glued on top of it. I would carefully try to remove the rubber and either unsolder the metallic cap or try to remove the dent, that I'm sure exists under the rubber, without unsoldering it.

Are we talking about the same thing? I'm not sure what it's called, but I mean the button to the right of the central directional pad. The PB614 manual calls it the forward button.

Edit: attached photo of board

[nhedgehog]

No we are not, I made a red circle around it. Are you sure about the other button?

The button you are pointing is different to repair. Did you try to press it a couple of times. How does it respond?

[DoomsdayDog]

Originally Posted by nhedgehog

No we are not, I made a red circle around it. Are you sure about the other button?

The button you are pointing is different to repair. Did you try to press it a couple of times. How does it respond?

The button I pointed: it feels normal when I press it down, but the LED tester shows that the circuit is always closed, as if the button is always pushed down.

The opposite button and the power button: also feel normal to touch. LED tester shows that the circuit closes only when I push these buttons, so they are not stuck.

The round buttons on the directional pad: I don't know how to test these because the four pins I was using to test the other buttons are not exposed. These buttons also feel normal to the touch now that I have freed them from the front cover (but yes previously they felt weird through the plastic pad).

[nhedgehog]

You didn't free them before. Try to click them several times especially the right D-pad button. After that try to boot up the device.

PS: One contact is the outer rim of the button, the other is probably on the other side of the board.

[DoomsdayDog]

Originally Posted by nhedgehog

You didn't free them before. Try to click them several times especially the right D-pad button. After that try to boot up the device.

OK, I see now. On my D-pad there are metal disks covered with metal caps (no sign of rubber), and all 5 metal caps are held on the D-pad with a transparent square of sticky tape (photo). It looks like one contact of the button is the inside region, the second is the outer region, and the circuit is closed by the metal cap pressing down and bridging the inner and outer regions. I removed all metal caps, to prevent all the D-pad buttons from closing their respective circuits, but the device still won't boot.

So at this point the only abnormal button is the one I pointed, which has a closed circuit whether I press the button or not. So that must be the button that's stuck in the "ON" state. How do I take this button apart?

[nhedgehog]

That will be difficult. Unsolder it, see if the device boots up. If yes you can try to pry it somehow mechanically open and repair it or look for a replacement in the internet.

[DoomsdayDog]

Originally Posted by nhedgehog

That will be difficult. Unsolder it, see if the device boots up. If yes you can try to pry it somehow mechanically open and repair it or look for a replacement in the internet.

Time to learn soldering. I will be away for school and return for Christmas break, by which time I hope I will have the equipment and knowledge to remove the button - will it be OK to bump this thread after so long?

[nhedgehog]

No problem for me. Just make sure to get a soldering iron with a very small (needle) tip and a sharp cutter knife to get under the button. It is not as easy as it looks, since too high temperature can destroy the mainboard. Look for some SMD Soldering Tutorials.

[DoomsdayDog]

Originally Posted by nhedgehog

No problem for me. Just make sure to get a soldering iron with a very small (needle) tip and a sharp cutter knife to get under the button. It is not as easy as it looks, since too high temperature can destroy the mainboard. Look for some SMD Soldering Tutorials.

Alright, thanks again!