I am working on a custom design which only receives S/PDIF input from different devices and sends them to the USB host.
To get a known working starting point for my software adjustments, I got the xCORE-200 multichannel audio board and started removing things from the app_usb_aud_xk_216_mc app that I don’t need on my design. Specifically, I have:
- disabled the ADC (-DI2S_CHANS_ADC=0) and removed the ADC-related ports from the xn file
- removed the DAC from the code and xn file (merely disabling it results in compilation errors)
- removed the I2S_BCLK from code and xn file
- moved I2S_LRCLK to a different GPIO, as removing it from the code seems to screw up the timings
- replaced MCLK_IN2 and MCLK_IN with a clock derived from the reference clock
However, I am hitting a roadblock now. The only remaining port I want to get rid of is PORT_PLL_REF. When moving the signal to a different GPIO, I see USB errors from the kernel when the device is plugged in.
I don’t understand why that’s happening. As far as I can tell from the schematic, the PLL_SYNC signal goes into U10 (CS2100-CP), so if I don’t supply a clock, MCLK_XCORE, AUDIO_MCLK and MCLK_SPDIF won’t carry a valid clock. I thought this is okay, because:
- MCLK_XCORE goes into MCLK_IN and MCLK_IN2, which I don’t use
- AUDIO_MCLK goes into the analog parts, which I don’t use
- MCLK_SPDIF goes into SPDIF transmitting, which I don’t use
Code: Select all
(gdb) inf thr 8 tile core 0x00046af6 in XUD_TokenRx_Pid () 7 tile core (dual issue) Endpoint0 (c_ep0_out=<value optimized out>, c_ep0_in=<value optimized out>, c_audioControl=2147685634, c_mix_ctl=2147680514, c_clk_ctl=<value optimized out>, c_EANativeTransport_ctrl=<value optimized out>, dfuInterface=524072) at /usr/src/xmos/ws2/module_usb_audio/endpoint0/endpoint0.c:345 6 tile core (dual issue) XUD_SetReady_InPtr (ep=<value optimized out>, len=1, addr=<value optimized out>) at /usr/src/xmos/ws2/module_usb_audio/usb_buffer/usb_buffer.xc:732 5 tile core (dual issue) decouple (c_mix_out=2147680258) at /usr/src/xmos/ws2/module_usb_audio/usb_buffer/decouple.xc:810 4 tile core L0_UY () at /usr/src/xmos/ws2/module_spdif_rx/src/SpdifReceive.S:1636 3 tile core (dual issue) mixer1 (c_host=2147614722, c_mix_ctl=2147614978, c_mixer2=2147616258) at /usr/src/xmos/ws2/module_usb_audio/mixer/mixer.xc:363 2 tile core waitQuarter () at /usr/src/xmos/ws2/module_i2c_single_port/src/i2c-sp.xc:29 * 1 tile core (dual issue) clockGen (c_spdif_rx=2147615234, c_adat_rx=1414165324, p=66560, c_dig_rx=2147617026, c_clk_int=297504931, c_clk_ctl=2749171899) at /usr/src/xmos/ws2/module_usb_audio/clocking/clockgen.xc:822
Thankful for any hints,