Feature #4502
osmo-gsm-tester: support gpio controlled step attenuators of the LTHW main unit
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#2 Updated by dexter 10 months ago
- File pinouts.jpg pinouts.jpg added
- Status changed from Feedback to New
- Assignee changed from dexter to pespin
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