Question about StallGuard limits

[a.m.lovatt]

I'm using the EVAL-428 board with 246 driver chip. The stallguard profiler shows a steady and repeatable green bar at load of around 4 at the speed I want, except when stalled when it goes all red as expected.

However, when I use the supplied test application, the stall protection stops the motor after a few turns, even when on the least sensitive setting. The red bar does not increase visibily to anywhere near the limit I've set, it stays around half way and yet the motor stops anyway.

Can someone explain why that might be the case, or suggest what I'm doing wrong?

Thanks.

[Olav Kahlbaum (TRINAMIC)]

In the old version of the evaluation board firmware the stall value has only been checked once and if the limit was exceeded the motor was stopped. In the meantime we found out that it is better to check the stall value always twice in order to make it reliable. Newer firmware (that can be downloaded from our website) does it this way.
So, if you are designing your own board you should also do so in your firmware. Please see the TMC428 evalboard fimrware source code (which can also be found on our website now).
Sorry for this inconvenience.

[a.m.lovatt]

Thank you.

Sending $FF to the evaluation board without updating I get EVAL428 V3.1

The website doesn't obviously label firmware versions, so I'm not sure of the latest version. Also, I'm not sure how to update the firmware - the manual makes a passing reference to an Atmel ISP which of course I don't have, presuming the evaulation board would be self sufficient.

[Olav Kahlbaum (TRINAMIC)]

I have updated the versions on the website once again yesterday. The only way to reprogram an evaluation board is via an Atmel ISP programmer (as an additional bootloader won't fit into the ATmega8).
Unfortunately the old firmware as well as the new one will report "EVAL428 V3.1" (it more reflects the hardware version of the board). But the behaviour of your board looks as if it had old firmware.

It will also be necessary to reprogram the TMC428 configuration datat inot the EEPROM range of the ATmega8 after reprogramming the flash ROM of it. This can be done either by loading one of the *.428 files using the EVal428EEP.exe program via the serial interface (this files can all be found on the CD) or by programming the .eep file into the EEPROM range of the ATmega8 using the Atmel ISP (the .eep file is generated when building the firmware).