JTAG

Introduction

A JTAG interface is designed for on-chip debugging. It is used to program that do not have a means to upload software via USB already. For short; if you want to upload your own software or want to do serious paparazzi development work, the you need a cable like this.

JTAG Cable overview

There are multiple Paparazzi-compatible devices available that support JTAG. Below you find a list of JTAG devices that you can use in combination with e.g. a Paparazzi Lisa/M board.

FLOSS JTAG

The FLOSS JTAG is based on an FTDI chip that allows two simultaneous USB connections, which means that FLOSS JTAG allows JTAG and UART/COM connections.

Let's take a look at upper side of the board. It contains JTAG connector (which is connected on photo) and two sets of RX/TX LEDs for JTAG and UART/COM interface separately. The JTAG connector is 2x5 pins, 0.05-inch pitch, and is compatible with the Samtec FFSD-05-D-06.00-01-N-RW-R ribbon cable.

On the other side of the board there is 4 pin UART/COM connector, which contains: Ground (black), TX (yellow), RX (orange) and +5V (red)

Usage of board is pretty simple: JTAG can be used to upload firmware into the board and/or repair board with broken bootloader, and UART/COM interfaced can be used to make "COM port style" connection to the board. COM connection can be used for example for telemetry debug.

More info available on the randomprojects.org wiki.

Black Magic Probe

Full info about the Black Magic Probe is available at the Black Sphere Technology website.

To use Black Magic Probe instead of FLOSS-JTAG or Luftboot, append the following string to the upload command:

On Linux:

FLASH_MODE=JTAG BMP_PORT=/dev/ttyACM0

On Mac OS:

FLASH_MODE=JTAG BMP_PORT=/dev/cu.usbmodem<serial>

There are good Reasons to use Black Magic Probe Mini instead of FLOSS-JTAG: It just has much more options and cost less.

• No need for OpenOCD as BMPM has a built in GDB server
• Orders of magnitude faster as all the high speed protocol logic happens on the built-in STM32
• Supports Serial Wire Debug (SWD)
• Supports tracing using the SWD trace pin
• No need for loading and unloading of FTDI drivers on Mac OS X

How to use Debugging features

A page describing on how to start debugging using the BlackMagic probe cable can be found here JTAG: DevGuide/JTAG-Debug

Upgrade BMP firmware

 git clone git://blackmagicdebug.git.sourceforge.net/gitroot/blackmagicdebug/blackmagicdebug
 cd blackmagicdebug/src
 make CROSS_COMPILE=~/sat/bin/arm-none-eabi-
 ../scripts/stm32_mem.py blackmagic.bin

FT2232 Dev Board

Use ftdi prog to change the Description String into: FLOSS-JTAG

Related articles

• DevGuide/JTAG-Debug - Developer's guide JTAG debugging
• Dev/Debugging - General debugging information

---

(*(oo)*), ,~