From: Xuebing Wang <xbing6@gmail.com>
To: Nicolin Chen <nicoleotsuka@gmail.com>, alsa-devel@alsa-project.org
Cc: niranjan Patil <Niranjan.Patil@infocus.com>,
fabio Estevam <festevam@gmail.com>,
richard Jiang <Richard.Jiang@infocus.com>
Subject: Freescale iMX6SL SSI (I2S master mode) Rising edge vs Falling edge
Date: Thu, 28 May 2015 15:02:31 +0800 [thread overview]
Message-ID: <5566BD87.6040505@gmail.com> (raw)
Nicolin and alsa-devel community:
Source code in fsl_ssi.c shows below in function fsl_ssi_set_dai_fmt():
-----------
switch (fmt & SND_SOC_DAIFMT_FORMAT_MASK) {
case SND_SOC_DAIFMT_I2S:
... ...
/* Data on rising edge of bclk, frame low, 1clk before data */
strcr |= CCSR_SSI_STCR_TFSI | CCSR_SSI_STCR_TSCKP
| CCSR_SSI_STCR_TXBIT0 | CCSR_SSI_STCR_TEFS;
break;
-----------
According to iMX6SL reference manual, 'TSCKP = 1' means "Data clocked
out on *falling* edge of bit clock." (for I2S master mode), rather than
"Data on rising edge of bclk in the comments". This means this comment
in the source code is *partially* WRONG, am I correct?
However, RSCKP is = 1 (for receiving), it means "Data latched on rising
edge of bit clock", which is correct.
Also, I am not sure why there is inconsistency in iMX6SL reference
manual (48.9 SSI Memory Map/Register Definition), that TSCKP = 1 (for
transmitting) is FALLING_EDGE, but RSCKP = 1 (for receiving) is RISING_EDGE.
Note: SSI (I2S master mode) works perfect on my hardware, I did not
observe anything wrong.
Thanks.
--
Xuebing
next reply other threads:[~2015-05-28 7:02 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-05-28 7:02 Xuebing Wang [this message]
2015-05-28 7:09 ` Freescale iMX6SL SSI (I2S master mode) Rising edge vs Falling edge Nicolin Chen
2015-05-28 7:15 ` Xuebing Wang
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