Problems with keypad on Cherry ST-2000U card reader

[Johannes Zarl]

Hi,

I recently got my fellowship card and now try to get a working setup. My first 
tries with a ReinerSCT cyberjack that I had lying around did not get me 
anywhere, so I bought a Cherry ST-2000U which looked like it should work with 
the internal CCID driver. The reader is "mostly" working, i.e. I can't get the 
pin entry via internal keypad to work.

Symptoms:
Using pcscd (and therefore pinentry on my pc), the reader works flawlessly.
Using the internal driver (after stopping pcscd), "gpg --card-status" works 
fine.
When an operation needs the pin, the reader switches correctly into pin entry 
mode (judging by the leds). Regardless of whether I enter the correct pin or 
an incorrect one, after pressing the "ok"/green key, the operation is aborted.

Using gpg (not gpg2), I get the following message after hitting "ok":

gpg: sending command `SCD PKDECRYPT' to agent failed: ec=6.55

Except for this additional message, gpg and gpg2 behave exactly the same.

I'm using the following versions (on Debian sid):
gpg (GnuPG) 1.4.14
gpg (GnuPG) 2.0.21
libgcrypt 1.5.3

Card info:
Version ..........: 2.0
Manufacturer .....: ZeitControl

Card reader (lsusb):
Bus 006 Device 003: ID 046a:003e Cherry GmbH SmartTerminal ST-2xx

Any idea what could be the problem or how I can debug the issue?

Thanks,
  Johannes