Why are we using a nonstandard debug header?

[mck1117]

There exists a standard debug header that is:

• physically smaller
• industry standard (no more eBay pinout mysteries and fake programmers)
• keyed (impossible to plug in backwards)

Here's the doc on the Cortex debug headers. We'd be interested in the "Cortex Debug Connector (10-pin)" described on page 2. http://infocenter.arm.com/help/topic/com.arm.doc.faqs/attached/13634/cortex_debug_connectors.pdf

When the ST-LINK/V3 comes out soon, we'll be able to buy just the $11 programmer: https://www.digikey.com/product-detail/en/stmicroelectronics/STLINK-V3MINI/497-19530-ND/10266291

Today, the connector can be used with an official ST-LINK/V2: https://www.digikey.com/product-detail/en/stmicroelectronics/ST-LINK-V2/497-10484-ND/2214535 Plus an adapter to the 1.27mm 10-pin: https://www.digikey.com/product-detail/en/olimex-ltd/ARM-JTAG-20-10/1188-1016-ND/3471401

[mck1117]

update: Mouser has the stlink-v3 in stock! https://www.mouser.com/ProductDetail/STMicroelectronics/STLINK-V3MINI?qs=mAH9sUMRCtvrXm%2FF%2FC0CYg%3D%3D

[mck1117]

And here's an example connector we could put on the board: https://www.digikey.com/product-detail/en/samtec-inc/FTSH-105-01-F-DV-007-K/SAM15640-ND/6693339 It's quite small, only requires around 6x7mm of board space.

[DonaldBecker]

The argument for the current connector is: A USB dongle ST-Link v2 is $2 The connector is inexpensive, at around $0.25 The connector pins are enclosed, making it safe for poking around. Both 5V and 3.3V can be supplied through the connector, allowing a single debugging cable

The argument against is The footprint is huge Using a female header requires the ST-Link dongle to plug directly into the board Doubled pins are certainly not needed.

Alternative are Omitting programming header completely

• DFU for installation and updates is good enough for end users TagConnect footprint
• Tiny footprint, zero cost
• Expensive commercial cable or fiddly home built cable needed. Changing the suggested header to a male pins
  • Inexpensive, and allows using cheap cables to the programmer
  • Still the same footprint size, and exposed 5V pins sticking up is risky Changing the header to shrouded male pins
• Keyed ribbon cable to avoid reverse connection, mitigates exposed pins, inexpensive
• Effectively even bigger footprint (no flat components allowed in surrounding area) 3 or 4 pin SWD header in the Discovery board pattern
  • Inexpensive, smaller, does everything Standard JTAG, 2.54 or 1.27 spacing
    • More pins, none of which add value ST-Link v3 header
      • Programmer is only about $10
      • Expensive header $3.20 ea
      • Very little benefit for extra pins
      • Very new and still uncommon

Right now I'm leaning to a 3 or 4 pin SWD only connector, with a leg-less TagConnect footprint. Perhaps with a 2x2 SMD pin header rather than the 1x4 Discovery header for space savings That provides almost complete debugging at minimal cost, usable with the existing ST-Link debuggers.

[jharvey]

This is obsolete, suggest closing this issue. We appear to have both standard and less standard programming headers now.

[mck1117]

We have 10 pin cortex now?