Ergodox: Left half does not work, right half works fine

[v6ak]

I have Ergodox kit from Falbatech. The right half is completely soldered (and flashed with the TMK firmware) and works fine if there is a TRRS cable connected. The left half, however, does not work at all.

The left half is soldered except the switches. I've tested it by shorting corresponding pins of a switch. This has worked for the right half.

Just after start, the red Teensy LED lights for about one second. I don't know if it is indication of some success, or indication of some failure.

What I've tried:

* The TRRS cable is OK. (Measured by multimeter, all four pins are OK, plus there is no short.)
* The connection between Teensy and I/O Extender (“IOX”) seems to be done through two wires only. The other pins seem to be unused. (I've used multimeter to verify that the connection between a Teensy pin and corresponding IOX pin is OK, so I've verified cable, connector, PCB and their interconnections.)
* There is no current going to the switch holes. On the right side, I measure about 4.3V or 4.5V, depending on what side of diode I am measuring. (Bot obvious reasons.) On the left side, I can't find any current here.
* This excludes reversed diodes issue. If it was just issue of reversed diodes, I would measure some current at least when measuring at one of the sides of the diodes.


What I am not sure:
* How to determine if there is some current going to the left half? Should I measure AC here? It shows something under 1V.

Some possible conclusions:

* Teensy is faulty.
* Teensy is OK, but TMK just realized that the other side is faulty and subsequently stopped the I2C interconnection.


What are your suggestions?

[tp4tissue]

i remember on mine, mine didn't work properly till i soldered in the diodes.

also that capacitor.

[v6ak]

I've soldered all the diodes, so missing diodes is not my issue. (Assuming that you don't mean LED diodes, which is the part I don't have at all and I currently don't plan adding them.) The only thing that is not soldered are switches. But shorting corresponding PCB points should emulate pressing the missing mechanical switch, there should be no electrical difference between regular switch and this emulation. Note that this switch emulation has worked on the right half.

I also have soldered the capacitor and shorted the two points, as mentioned at https://keyboard-configurator.massdrop.com/ext/ergodox/assembly as an optional step .

I've also re-checked that there are no resistors to be soldered on the left side.

I've also verified that two IOX pins (12+13? – not sure about the numbering) are not only connected to the Teensy (D0+D1), but they are also connected so some pins of the AVR μcontroller.

I've found program hid_listen that allows me to see the debug output, which has told me more. (I've added several printlns in order to know more.)

I've found some details on blinking: According to the source code and its debug output, it should blink on start and on I2C success. Well, it does not blink on start if TRRS is not connected, because matrix_init»init_mcp23018»i2c_start blocks (probably in while(!(TWCR & (1<<TWINT))), so matrix_init»ergodox_blink_all_leds is never reached. Second, it should also blink on successful I2C connection. The successful connection never happens, even with the right end-to-end wiring.

It seems that D0+D1 pins are OK: The μcontroller can detect they are shorted. (When no TRRS cable is connected, they are shorted.) Well, they are at least partially OK, as this means that one of them is able to work as output and the other is able to work as input. It does not tell us whether they are able to do both operations.

Should I post some photos? I've tried to take some photo, but I was unable to get it sharp, so it will require more effort (or a different camera).

[tp4tissue]

well, we can't check the soldering better than your eyes could.. haha..

I guess you could go over the controller pins youpve already soldered and check for cold joints..

[v6ak]

* I don't have much soldering experience, but capacitor is reportedly soldered correctly.
* Teensy and IOX is probably also soldered OK, as suggested by ohmmeter.
* Teensy pins D0 and D1 seem to be OK. (It can detect short between them.)
* I don't suspect capacitor to be faulty.
* So, the faulty part it probably the IOX.

I can order a new IOX for about $4 (incl. shipping). However, I'd like to ensure that IOX is the faulty part before desoldering the old one if there is an easy way to do so. (Desoldering a 28-pin chip is not something I have experience with.)

[v6ak]

So, it seems that the only issue was missing jumps near TRRS connectors. The following assumption done in my inital post was wrong:

The connection between Teensy and I/O Extender (“IOX”) seems to be done through two wires only. The other pins seem to be unused.

After soldering the four missing jumps, it seems to have started working.

[tp4tissue]

So, it seems that the only issue was missing jumps near TRRS connectors. The following assumption done in my inital post was wrong:

The connection between Teensy and I/O Extender (“IOX”) seems to be done through two wires only. The other pins seem to be unused.

After soldering the four missing jumps, it seems to have started working.

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