Hi Folks,
First time poster, long time lurker. I've been working on a motor/sensor platform that has gone through many iterations. The latest design uses a single teensy as the brains of the motor control and a raspberry pi as the webserver/pretty interface.
Obviously moving into manufacture there are plenty of perks to a custom board. With that in mind I had a small development board made up to test which has worked out pretty good (I had an issue where pin 33 was too low due to an opto-isolator which prevented reprogramming - this was fixed by cutting the trace). So I've had a little bit of success with a custom pcb with an MK20 + PJRC Mini54 combination.
Today I've been testing the master board from my project, shematic attached. I've been able to reprogram it multiple times until the last 20 minutes. I was at the point of testing the Raspberry Pi -> MK20 connection. There are two points of connection. The raspberry Pi will communicate with the MK20 over USB but also have GPIO access to the program and reset lines of the custom pcb to ensure the MK20 can be reprogrammed under an error situation.
Unfortunately this test seems to have killed my board. The raspberry Pi I used is slightly suspect (it's booting up un-reliably). This leads me to think that potentially the Pi has placed 5V on the program or reset line of the MK20/Teensy (just a guess). There were no sparks, no smoke and nothing exciting seemed to happen. I simply can't get usb traffic from the board - it appears to be unresponsive.
Here's what I'm seeing:
Power - All Correct. 3v3 is fine, stable. 5V is USB and stable
Rest Line - 20KHz (50uS) pulses on the reset showing the MK20 is resetting the line as if it hadn't been programmed before - confirmed by grounding the MINI54 Reset line
Program Line - changes on button press (high to low)
SWD Lines - Mini54 is transmitting clock and data - confirmed with oscilloscope (not sure if the data is correct but the lines are toggling)
Pin 33 - High
On first power up if I press the Prog button then the mini54 attempts to program the MK20 over SWD. However the Reset line continues to pulse after the MINI54 has released it.
I can't figure out what the cause or solution is. Everything appears to be working as it should but the bootloader isn't loading onto the MK20 (by the way my schematic shows an MK20 for Teensy 3.0 but I'm actually using the Teensy 3.1 chip).
I'm also not sure why, or even if, the raspberry pi is the cause. It doesn't appear to be doing anything.
I have another 4 boards made up that I haven't tested yet. I want to solve this issue or at least understand how it happened to be able to prevent it in the future.
Attachment: Link - Sorry the attachment for the schematics is over 15mB. (I used RS Components Design Spark - I don't recommend it *sigh* )
First time poster, long time lurker. I've been working on a motor/sensor platform that has gone through many iterations. The latest design uses a single teensy as the brains of the motor control and a raspberry pi as the webserver/pretty interface.
Obviously moving into manufacture there are plenty of perks to a custom board. With that in mind I had a small development board made up to test which has worked out pretty good (I had an issue where pin 33 was too low due to an opto-isolator which prevented reprogramming - this was fixed by cutting the trace). So I've had a little bit of success with a custom pcb with an MK20 + PJRC Mini54 combination.
Today I've been testing the master board from my project, shematic attached. I've been able to reprogram it multiple times until the last 20 minutes. I was at the point of testing the Raspberry Pi -> MK20 connection. There are two points of connection. The raspberry Pi will communicate with the MK20 over USB but also have GPIO access to the program and reset lines of the custom pcb to ensure the MK20 can be reprogrammed under an error situation.
Unfortunately this test seems to have killed my board. The raspberry Pi I used is slightly suspect (it's booting up un-reliably). This leads me to think that potentially the Pi has placed 5V on the program or reset line of the MK20/Teensy (just a guess). There were no sparks, no smoke and nothing exciting seemed to happen. I simply can't get usb traffic from the board - it appears to be unresponsive.
Here's what I'm seeing:
Power - All Correct. 3v3 is fine, stable. 5V is USB and stable
Rest Line - 20KHz (50uS) pulses on the reset showing the MK20 is resetting the line as if it hadn't been programmed before - confirmed by grounding the MINI54 Reset line
Program Line - changes on button press (high to low)
SWD Lines - Mini54 is transmitting clock and data - confirmed with oscilloscope (not sure if the data is correct but the lines are toggling)
Pin 33 - High
On first power up if I press the Prog button then the mini54 attempts to program the MK20 over SWD. However the Reset line continues to pulse after the MINI54 has released it.
I can't figure out what the cause or solution is. Everything appears to be working as it should but the bootloader isn't loading onto the MK20 (by the way my schematic shows an MK20 for Teensy 3.0 but I'm actually using the Teensy 3.1 chip).
I'm also not sure why, or even if, the raspberry pi is the cause. It doesn't appear to be doing anything.
I have another 4 boards made up that I haven't tested yet. I want to solve this issue or at least understand how it happened to be able to prevent it in the future.
Attachment: Link - Sorry the attachment for the schematics is over 15mB. (I used RS Components Design Spark - I don't recommend it *sigh* )