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Feature #4502

osmo-gsm-tester: support gpio controlled step attenuators of the LTHW main unit

Added by pespin 7 months ago. Updated 7 months ago.

Status:
New
Priority:
Normal
Assignee:
pespin
Target version:
-
Start date:
04/18/2020
Due date:
% Done:

0%

Spec Reference:

Description

Patch [1] implements initial support for RF channel emulator for ENB objects. We should add support for the step attenuator connected to the sysmocom's osmo-gsm-tester setup.

According to laforge , dexter has written example code for this years ago.

[1] https://gerrit.osmocom.org/c/osmo-gsm-tester/+/17847

pinouts.jpg View pinouts.jpg 985 KB dexter, 04/20/2020 09:48 AM
4086

History

#1 Updated by pespin 7 months ago

  • Status changed from New to Feedback
  • Assignee changed from pespin to dexter

Assigning to dexter to provide here with the information he has available for the device.

#2 Updated by dexter 7 months ago

  • File pinouts.jpg pinouts.jpg added
  • Status changed from Feedback to New
  • Assignee changed from dexter to pespin
4086

The step attenuator is controlled via the GPIO interface of the APU directly. As far as I know there are 4 attenuators. The synchronous serial interface is wired in parallel while the latch enable lines are wired individually. The attenuation value is shifted into the internal shift-register of all attenuator at once. The latch enable line latches the value to the outputs of the shift register to the register that controls the attenuation.

There is a git repository with a driver and a utility
git.sysmocom.de/sysmo-att-ctrl

The attenuator is an ZX76-31R5-SP+ from Mini-Circuits.

As far as I remember the GPIO chip in the APU is an NCT5104, some Info about the driver can be found here: https://github.com/tasanakorn/linux-gpio-nct5104d/pull/3/files

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