ECP5 FPGA autodetect: irlen is set to wrong value

I’m working with a Colorlight 5A-75E [1], in combination with an Altera USB Blaster [2], using this guide [3].

When I use a minimal config file, I get this result:

$ cat myopenocd.cfg

adapter driver usb_blaster

$ openocd -f ./myopenocd.cfg

Open On-Chip Debugger 0.11.0

Licensed under GNU GPL v2

For bug reports, read

openocd.org/doc/doxygen/bugs.html

Info : only one transport option; autoselect ‘jtag’

Info : Listening on port 6666 for tcl connections

Info : Listening on port 4444 for telnet connections

Info : No lowlevel driver configured, using ftdi

Info : usb blaster interface using libftdi

Info : This adapter doesn’t support configurable speed

Warn : There are no enabled taps. AUTO PROBING MIGHT NOT WORK!!

Info : JTAG tap: auto0.tap tap/device found: 0x41111043 (mfg: 0x021 (Lattice Semi.), part: 0x1111, ver: 0x4)

Warn : AUTO auto0.tap - use “jtag newtap auto0 tap -irlen 2 -expected-id 0x41111043”

Error: IR capture error at bit 2, saw 0x3fffffffffffff05 not 0x…3

Warn : Bypassing JTAG setup events due to errors

Warn : gdb services need one or more targets defined

Now I set irlen to 8, and then it works:

$ cat myopenocd.cfg

adapter driver usb_blaster

jtag newtap auto0 tap -irlen 8 -expected-id 0x41111043

$ openocd -f ./myopenocd.cfg

Open On-Chip Debugger 0.11.0

Licensed under GNU GPL v2

For bug reports, read

openocd.org/doc/doxygen/bugs.html

Info : only one transport option; autoselect ‘jtag’

Info : Listening on port 6666 for tcl connections

Info : Listening on port 4444 for telnet connections

Info : No lowlevel driver configured, using ftdi

Info : usb blaster interface using libftdi

Info : This adapter doesn’t support configurable speed

Info : JTAG tap: auto0.tap tap/device found: 0x41111043 (mfg: 0x021 (Lattice Semi.), part: 0x1111, ver: 0x4)

Warn : gdb services need one or more targets defined

Why does openocd choose 2 as default for irlen?

Where in the source of openOCD can this be changed?

[1] chubby75/5a-75e at master · q3k/chubby75 · GitHub

[2] www.aliexpress.us/item/2251800524323433.html

[3] https://forum.linuxcnc.org/27-driver-bo … ght-5a-75e

Unsure; maybe poke around their info https://openocd.org/ and/or support?