Unable to detect a bare STM32L412K8T6 from a breakout board

[lukebayes]

• Programmer/board type: Stlink/v2 (official blue and white version)
• Programmer firmware version: V2J35S7 STM8/STM32 Debugger
• Operating system: Linux

Distributor ID: Ubuntu
Description: Ubuntu 19.10
Release: 19.10
Codename: eoan
Linux beefcake 5.3.0-29-generic #31-Ubuntu SMP Fri Jan 17 17:27:26 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux

• Stlink tools version: v1.5.1-50-g3690de9
• Stlink commandline tool name: st-info, st-flash and st-util
• Target chip: STM32L412K8T6 on a bare QFP32 breakout board.

In a terminal, run:

st-info --probe

Output:

Found 1 stlink programmers
 serial: xxx[manually obscured]0267
openocd: "\x50\x3f\x72\x06\x77\x3f\x54\x54\x35\x37\x02\x67"
  flash: 0 (pagesize: 0)
   sram: 0
 chipid: 0x0000
  descr: unknown device

When I attempt to flash & debug from the STM32CUBEIDE (Eclipse), using SWD debugger get a pop-up error with the following:

Error in initializing ST-LINK device.
Reason: (4) No device found on target.

Expected/description:
Expected the device to be found and flashed.

I'm almost certainly missing something simple, but I've been at this for a couple of days now and can't seem to find the secret key.

I have tried many different wire and configuration combinations.

I'm currently using the 20 pin connector from the STLINK/V2 as follows:

STLINK/V2	STML412Kx LQFP32
1	1/VDD
2	NC
3	32/VSS
4	32/VSS
5	NC
6	32/VSS
7	23/SWDIO
8	32/VSS
9	24/SWCLK
10	32/VSS
11	NC
12	32/VSS
13	26/SWO
14	NC
15	NC
16	NC
17	NC
18	32/VSS
19	NC
20	32/VSS

I'm powering the board with either an LM317T configured to give me 3.3V (reading at 3.4V), or directly from the STLINK at 3.1V.

I have 100nF caps bridging VDD and VSS next to each power line.

I'm (hopefully) using the internal oscillator.

Other than that, it's a bare IC that's on a breakout board, which is attached to a breadboard.

I've been able to successfully flash and debug the STM32L412 Nucleo-32 (with built-in STLINK) over USB on this computer with no issues at all.

Any tips for flashing (and debugging) a bare chip would be greatly appreciated!

[lukebayes]

Problem solved.

The root issue was that I was reading the connector pinouts backwards, and I've had some incorrect diagrams floating around. The real confusion is whether one should read these pinouts as if looking into the ribbon cable or looking down at the header?

For posterity and anyone else struggling with the same issue, here's the JTAG connection table for an STM32L412K8T6 (LQFP32/UFQFPN32) board and the official ST-Link/V2 debugger and programmer 20-pin connector.

The best connector diagrams I found are at STM32-Base.

STLINK/V2	STML412Kx LQFP32
1	NC
2	NC
3	TRST/27
4	GND
5	TDI/25
6	GND
7	TMS/SWDIO/23
8	GND
9	TCK/SWCLK/24
10	GND
11	NC
12	GND
13	TDO/SWO/26
14	GND
15	NRST/4
16	GND
17	NC
18	GND
19	VDD/3.3V PWR
20	GND