Eric N. Johnson (ACD)
ejohnson at acdstar.com
Wed Apr 13 05:38:20 EST 2005
Has anyone been able to use an I2S audio DAC connected to a Programmable
Serial Controllers (PSC) on the Freescale MPC5200 CPU working under Linux?
The kernel included in the DENX ELDK v3.1.1 has two drivers:
i2s_ring.c and i2s.c.
The ring driver appears to be RX only, and the i2s.c driver causes the FEC
ethernet to hang at startup. I've read some previous mailing list messages
that suggest there are issues with bestcomm and i2s support.
We've tried adapting the i2s_ring.c driver for our needs. By default, it
only has a receive task. It partially initializes the port, and we see
appropriate waveforms on the MCLK, CLK, and FRAME lines, but have not been
able to transmit data.
The stock i2s.c driver hung the boot sequence, but if we comment out the
bestcomm startup code, it at least completes the boot cycle. Again we see
appropriate waveforms on the MCLK, CLK, and FRAME lines. If we feed data
to the device (after performing the port setup IOCTLs), we see a 750 us
burst of data every 45 ms or so.
Is it feasible to send 44.1 or 48 KHz 16-bit audio this way or is the PSC
only usable for lower data rate applications?
Eric Johnson, Electrical Engineer
Advanced Communication Design
7901 12th Avenue South
Bloomington, MN 55425
Ph: 952-854-4000 Fax: 952-854-5774
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