PCM1795 control channel readback unstable

LO WING SUM

Other Parts Discussed in Thread: PCM1795

Hello, I 'm a new user of PCM1795 and this forum. I would like to use SPI to read and verify registers using Beaglebone black SPI, but the readback is unstable(readback word is not what was command to write) . The circuit diagram is attached. SCL is made by the McASP pin P9_25 of the beaglebone black. the remaining SPI is connected to SV2. Please help

over 11 years ago

0 Don Dapkus over 11 years ago

TI__Guru**** 189401 points

Hi, Sum,

Welcome to e2e, and thanks for your interest in our products! I haven't personally used this combination, so hopefully someone in the Community will chime in with their experience.

In the meanwhile, the first thing that comes to mind is voltage levels. Since the PCM1795 runs off 5V, the logic thresholds on the digital pins are TTL levels. Maybe the BeagleBoneBlack can't output TTL logic levels?

-d2

0 LO WING SUM over 11 years ago in reply to Don Dapkus

Prodigy 20 points

since from specifications, input voltage for digital input range from -0.3 to 6.5V, I'll take 3.3V as acceptable level?

0 Don Dapkus over 11 years ago in reply to LO WING SUM

TI__Guru**** 189401 points

Hi, Sum,

The PCM1795 recognizes a logic low as any signal less than 0.8V, and a logic high as any signal greater than 2.0V. In between those values, is an undefined state, and should be avoided.

-d2

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PCM1795 control channel readback unstable