Teensy LC Bootloader Chip and JTAG on same PCB layout

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Lon Aylsworth

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Has anyone made a schematic of the LC PCB with the Bootloader chip and provisions for JTAG on same board. The layout I am planning is to make 200 PCB's with the Bootlaoder and then production without the booatloader. So, the configuration would be an either or layout but only one PCB design. Either the Bootloader or the JTAG. Agency testing is expensive and I can get two for the price of one through the agency testing if this works out well. Many thanks from a first timer on this forum. Lon
 
Not that I've seen.

There is a posting here on how to cut traces to break out the SWD pins on a T3. Likely similar to LC.
This SWD... no one much uses JTAG anymore.
SWD is GND, target Vcc, data, clock.
Several inexpensive SWD pods available.

Opinion: at 200ea, I'd use the Teensy bootloader chip.
 
I guess I am showing my age with JTAG. I am planning to use the Teensy bootloader for the first 200 but not the 1,000's per month forecast after that. I looked up SWD, never heard of that before... That's the way I will proceed. Many thanks for the kind response stevech.
 
Good.
JTAG eats up a lot of I/O pins! Not so, SWD. The SWD "trace" pin is optional.

Of course, you an install a UART or SPI bootloader in the flash and use that instead of SWD or the LC's USB bootloader chip.
 
You can design a board to have both a teensy boot loader and a SWD header (aka 10 pin Cortex Debug Connector). Then populating the boot loader is optional.
 
Non-standard, but you can use a smaller pin count connector for SWD. But you'd need an adapter to 10 pin or 20 pin in order to mate with standard SWD pods. I use the $25 ST-Link v2. I assume it will work with any MCU brand conforming to the SWD standard.
 
Some distributors like Digikey also offer chip programming service. I haven't personally used this, so I don't know what they charge, but maybe it'd be competitive with the cost of that extra connector and whatever labor is involved with plugging in a programmer. But even if you go that route, having unpopulated locations for the header and bootloader chip won't hurt (other than the very minor cost of extra PCB space).
 
PaulStoffregen said:
Some distributors like Digikey also offer chip programming service. I haven't personally used this, so I don't know what they charge, but maybe it'd be competitive with the cost of that extra connector and whatever labor is involved with plugging in a programmer. But even if you go that route, having unpopulated locations for the header and bootloader chip won't hurt (other than the very minor cost of extra PCB space).
Click to expand...

We actually did this where I work a few years ago for some PCB boards we needed a few hundred copies of, and didn't want to manually burn ourselves (we don't really do electronics here anyway). If I'm reading the old quote right, it looks like the charge was a flat $50 for up to 200pcs, or $125 for 500pcs (this was a PIC18). YMMV, but a point of reference. We sent them the hex file, they sent a couple test chips for approval, then the final order went through.
 
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