Blew up 2 Teensy LCs

[P Dobson]

Hi,

I have been writing code to run MAX7219s driving 7 segment displays connected to X-Plane via the "Flight Sim Controls" interface. This all worked and I got 7 MAX chips to run from a Teeny LC. Then I wanted to add a further 2 off MAX chips, so I started a second SPI port as a single port can only drive 8 MAX chips using the LEDcontrol Library. At this point when I tried to program the code the Teensy LC stopped appearing as a connection via the USB port. I tried all the suggestions in other posts and a second computer to no avail. Unfortunately I tried a second Teensy LC and the same thing happened. But if I fit a Teensy 3.2 it programs and runs but the second SPI port is not supported by the Teensy 3.2. I have checked the voltages on the interface port and they are all correct at 3.3v so I should not have overvolted the LC chip.

Has anyone any clue what I did wrong?
Can I get a second SPI port to run on a Teensy 3.2?
I now have a collection of Teensys that are dead. Would PJRC take these back for repair for me?

Code enclosed (not very efficiently written).

Kind Regards, Pete Dobson.

 

[PaulS]

Could it be a powerconsumption issue?
I suppose the MAX7219's and 7-segment displays are powered from the Teensy LC Vin pin [which is effectively Vusb]?

You stated that the problems arose when hooking 2 more MAX7219's to the Teensy LC. Could it be that too much current is drawn from the USB power?

I'm a bit confused about the number of MAX7219's and displays you are using. The first line of your code reads This sketch drives five 7-segment displays connected via a Max7219. Above you state I got 7 MAX chips to run from a Teeny LC. This means a total of 35 7-segment displays?

Are you able to share a schematic/wiring diagram how all parts are connected? How many 7-segment displays are connected to each MAX7219?

Paul

 

[P Dobson]

H, Thanks for your reply. I am monitoring the current using a USB current monitor board. Total current drawn is about 40mA so well within the capability of the USB port. I retested the voltages on all the Teensy LC pins and none are above 3.3v. I now think what happened is that I stupidly tried to program the Teensy LC as a Teensy 3.1, and I think that has killed the boot loader in the Teensy LC. So nothing is recognized on the USB port any more (even if I disconnect everything from the Teensy LC (except the USB port).

What is the procedure for reloading the Boot loader into the Teensy LC??

 

[PaulS]

What is the procedure for reloading the Boot loader into the Teensy LC??

I'm not aware of a procedure for reloading the bootloader on a Teensy LC.
What you can try is to insert the Teensy into the USB port of your PC while pressing and holding the program button before insertion and release the button a few seconds after insertion. Then try to upload the basic Blink program.

Paul

 

[P Dobson]

Hi Paul,

Thanks for the info, tried that to no avail. So really I was after the process used to load software/firmware into the Teensy when manufactured, maybe using a Freescale programmer?? or is the firmware already loaded when you buy the memory chips??

BR Pete Dobson.

 

[P Dobson]

Could it be a powerconsumption issue?
I suppose the MAX7219's and 7-segment displays are powered from the Teensy LC Vin pin [which is effectively Vusb]?

You stated that the problems arose when hooking 2 more MAX7219's to the Teensy LC. Could it be that too much current is drawn from the USB power?

I'm a bit confused about the number of MAX7219's and displays you are using. The first line of your code reads This sketch drives five 7-segment displays connected via a Max7219. Above you state I got 7 MAX chips to run from a Teeny LC. This means a total of 35 7-segment displays?

Are you able to share a schematic/wiring diagram how all parts are connected? How many 7-segment displays are connected to each MAX7219?

Paul

Hardware set up: each Max 7219 chip drives 5off 7 segment displays using efficient LEDs so current per display is very low and I have also turned down the brilliance to a low level. So when it worked via a single SPI buss there are 35off 7 segment displays. drawing approx. 50mA. I added a further 2off Max7219 chips driving 10 off 7 segment displays via what I thought was the second SPI buss on the Teensy LC (pins 0, 6, and 20). but during programming I forgot to reset the chip type from Teensy 3.2 to Teensy LC and tried to program an LC as a 3.2. If I re-plug the hardware from SPI1 to SPI0 and run it, the hardware works fine on a Teensy 3.2. But I believe I am right in saying the Teensy 3.2 does not support a second SPI buss??
Photo: The front unit is showing frequencies from aircraft Com Box 2 and the rear unit (upside-down) is showing DME Distance, speed and time. I think I need to do more work on the time calculation .

BR PD.

 

[PaulS]

So really I was after the process used to load software/firmware into the Teensy when manufactured, maybe using a Freescale programmer?? or is the firmware already loaded when you buy the memory chips??

Perhaps you're mistaken me for @PaulStoffregen, founder and owner of PJRC?

Paul

 

[P Dobson]

Ah yes, i wondered why his picture had changed ........

 

[PaulStoffregen]

Would PJRC take these back for repair for me?

Teensy LC was discontinued. Can't do much.

But I want to help. Best I can offer is if your order a new Teensy 4.0 or Teensy 4.1, I can offer you a 2nd unit for free. Hopefully that'll offset the loss of those those 2 Teensy LCs while also giving you a fresh start with currently available hardware.

Teensy 4.0 has 2 SPI ports (but 2 of the pins for the 2nd SPI port are bottom side pads) and Teensy 4.1 has 3 of them (but the 3rd is only on tiny bottom side pads). The Teensy 4.x boards also have a memory wipe and restore to known-good LED blink program, which didn't exist in the earlier Teensy products.

 

[P Dobson]

HI Paul,

Thanks very much for your input and offer. I suspect the problem with the Teensy LCs is entirely my own fault. Being in the UK I think delivery costs from the States is not very efficient and I can easily buy genuine Teensy4s direct from UK suppliers. I think from a technical point of view I was just interested to see if I could get the LCs to work again by reprogramming the bootloader Firmware in the Teensy. I have a number of programming devices for the AVR processor family but I don't know the process for the Freescale processors. Could you send me the Freescale boot loader firmware or is that being too cheeky of me??

BR Pete Dobson.

 

[P Dobson]

So just to round this session off. I bought 2 off Teensy 4s from the PiHut. And have designed a PCB to pick up the pins underneath for the second SPI port. Hopefully that should sort everything out. Though I am still interested in trying to reprogram the boot code in the Teensy LCs.

BR Pete D