Diy Teensy 3.6 bootloader trouble

[Rocketmanandrew]

I have been working on a custom project that uses the Teensy 3.6 schematic, the problem im having is that it doesn't show up on usb, i measured the voltage level of pin 10 on the MKL02, the one connected to the button and im only getting about 0.2 volts, i read to measure this on another post. When i power on the board i get a little blink from the LED (D1) and that's it, i can't seem to find anything wrong with my schematic, was wondering if yall had any ideas. Here is my schematic:

 

[Rocketmanandrew]

It seems like the bootloader isn't responding, nothing happens when i click the program button, the voltage level also doesn't go completely low.

 

[Angelo]

There are no capacitors associated with the quartz.
And there is no 100nF on every Vdd/Vss pins pair. They should be very close to the pins.

 

[jmarsh]

Just to confirm, the MKL02 is one you bought from PJRC and not just a random one from somewhere else?

 

[PaulStoffregen]

PJRC sells 2 different bootloader chips. They are physically the same, but come with different firmware. You need the T3 version. Please check your records from the purchase, as mistakenly buying the T4 version won't work with this hardware based on Teensy 3.6.

Of course a blank chip purchased from non-PJRC sources won't work.

 

[Rocketmanandrew]

Yes it looks like it was the T3 version.

 

[Rocketmanandrew]

It said on the crystal guidelines for the bootloader that i would only need crystal capacitors if my crystal was rated to 18pF the one i'm using
(this) only has 10 pF.

 

[PaulStoffregen]

0.2 volts on pin 10 (Program pushbutton) usually means the chip is blank.

Any chance this PCB was built by an assembly company? We have seen cases before where those companies will buy blank parts, and some of them will even lie when asked if they purchased from PJRC.

Edit: you can also get 0.2 volts if pin 15 is accidentally shorted to GND. It is supposed to be left unconnected, as is correctly shown on your schematic.

 

[Rocketmanandrew]

0.2 volts on pin 10 (Program pushbutton) usually means the chip is blank.

Any chance this PCB was built by an assembly company? We have seen cases before where those companies will buy blank parts, and some of them will even lie when asked if they purchased from PJRC.

I assembled it myself. I got 2 of the bootloader chips, so i tried putting the other one but no luck. Could it have somehow erased on start up? Got all the parts from digikey except the boot.

 

[PaulStoffregen]

Erase is only possible if debugger hardware is connected to pins 14 and 16. If those pins are left unconnected, the firmware can not be erased or altered.

 

[Rocketmanandrew]

I did the test again while connected usb and im getting like 0.5 volts on that pin now for some reason.

 

[PaulStoffregen]

If you touch the wire or connect resistors in the 100K to 1M range, you'll (probably) see the floating pin's voltage is very weak and easily influenced. This is a strong indication the chip either blank or not running its firmware (eg, pin 15 shorted to GND). Low voltage like 0.1 to 0.6 volts that's very weak is the indication the firmware isn't running. No specific voltage like exactly 0.2V is meaningful. The weakness of output is the main indicator.

You can also get strange low voltages if the chip is soldered incorrectly, or placed incorrectly like rotated 90, 180 or 270 degrees. In those cases, the chip doesn't get proper power but can try to partially power up because the 3.3V power is connected to another pin and bleeds through the ESD protection diodes inside the chip.

 

[Rocketmanandrew]

If you touch the wire or connect resistors in the 100K to 1M range, you'll (probably) see the floating pin's voltage is very weak and easily influenced. This is a strong indication the chip either blank or not running its firmware (eg, pin 15 shorted to GND). Low voltage like 0.1 to 0.6 volts that's very weak is the indication the firmware isn't running. No specific voltage like exactly 0.2V is meaningful. The weakness of output is the main indicator.

You can also get strange low voltages if the chip is soldered incorrectly, or placed incorrectly like rotated 90, 180 or 270 degrees. In those cases, the chip doesn't get proper power but can try to partially power up because the 3.3V power is connected to another pin and bleeds through the ESD protection diodes inside the chip.

Ok, ill try re flowing it and see if its getting the right amount of power.

 

[Rocketmanandrew]

If you touch the wire or connect resistors in the 100K to 1M range, you'll (probably) see the floating pin's voltage is very weak and easily influenced. This is a strong indication the chip either blank or not running its firmware (eg, pin 15 shorted to GND). Low voltage like 0.1 to 0.6 volts that's very weak is the indication the firmware isn't running. No specific voltage like exactly 0.2V is meaningful. The weakness of output is the main indicator.

You can also get strange low voltages if the chip is soldered incorrectly, or placed incorrectly like rotated 90, 180 or 270 degrees. In those cases, the chip doesn't get proper power but can try to partially power up because the 3.3V power is connected to another pin and bleeds through the ESD protection diodes inside the chip.

Reflowed and went over the pins with a soldering iron and it's now outputting 3.2V on the switch but still no usb connection, i'm going to see if maybe its a computer problem also.

 

[Rocketmanandrew]

Reflowed and went over the pins with a soldering iron and it's now outputting 3.2V on the switch but still no usb connection, i'm going to see if maybe its a computer problem also.

Iv tried a different computer and reflowing a bit more, but still no luck.

 

[PaulStoffregen]

On the bootloader chip page you can find links to make prior conversations about troubleshooting new circuit boards.

A common theme in those conversations is watching the voltage on the Program pin and Reset pin. Also pay attention to whether a low (but not zero) voltage on Reset is really a DC signal or the pin toggling rapidly because the main chip doesn't have a valid program and it repeatedly watchdog resets. Either way, when you hold Program low, you should see the bootloader chip hold Reset low. The 3.3V on Program confirms the bootloader at least started. Seeing Reset respond when Program is low can confirm it is continuously running.

Why you get no USB, I can't say. But you can find many of those prior conversations and see the reasons other people didn't have USB. Maybe your problem might be similar?

 

[Rocketmanandrew]

On the bootloader chip page you can find links to make prior conversations about troubleshooting new circuit boards.

A common theme in those conversations is watching the voltage on the Program pin and Reset pin. Also pay attention to whether a low (but not zero) voltage on Reset is really a DC signal or the pin toggling rapidly because the main chip doesn't have a valid program and it repeatedly watchdog resets. Either way, when you hold Program low, you should see the bootloader chip hold Reset low. The 3.3V on Program confirms the bootloader at least started. Seeing Reset respond when Program is low can confirm it is continuously running.

Why you get no USB, I can't say. But you can find many of those prior conversations and see the reasons other people didn't have USB. Maybe your problem might be similar?

Ok, i will try to see if i can read the reset pin, it's a little hard to get a connection to it since it's a small chip. If all else fails i know someone who has a scope and fancy test equipment so i can see what's going on.

 

[PaulStoffregen]

I really recommend using those links to read the many old conversations. Several people had problems with their PCBs similar to your latest info - the Program pin works but no USB communication. Many of them did eventually find the problem and spend time to explain. Your probably is probably similar to some of those stories. Reading those conversations can probably give you more ideas of how to check your PCB.

 

[Rocketmanandrew]

I really recommend using those links to read the many old conversations. Several people had problems with their PCBs similar to your latest info - the Program pin works but no USB communication. Many of them did eventually find the problem and spend time to explain. Your probably is probably similar to some of those stories. Reading those conversations can probably give you more ideas of how to check your PCB.

Yes, i'm going to do that also.

 

[Rocketmanandrew]

On the bootloader chip page you can find links to make prior conversations about troubleshooting new circuit boards.

A common theme in those conversations is watching the voltage on the Program pin and Reset pin. Also pay attention to whether a low (but not zero) voltage on Reset is really a DC signal or the pin toggling rapidly because the main chip doesn't have a valid program and it repeatedly watchdog resets. Either way, when you hold Program low, you should see the bootloader chip hold Reset low. The 3.3V on Program confirms the bootloader at least started. Seeing Reset respond when Program is low can confirm it is continuously running.

Why you get no USB, I can't say. But you can find many of those prior conversations and see the reasons other people didn't have USB. Maybe your problem might be similar?

So did did the test and it does the exact opposite, when i haven't clicked program its at about 0.4V but when i click it it goes up to 3.2V. This is very strange.

 

[Rocketmanandrew]

So did did the test and it does the exact opposite, when i haven't clicked program its at about 0.4V but when i click it it goes up to 3.2V. This is very strange.

I reflowed the whole chip and it worked . I think my solder paste is to old and is making bad connections. I probably should have just tried that in the first place.