I'm trying to get I2S audio output signals from AUDMUX5 on expansion connector (pins 88~100) to use an external DAC.
1) I commented the original mux configuration (to sgtl5000) into mx53_loco.c -> mx53_loco_pads
/* AUDMUX5 */
2) created the new pad mux into iomux-mx53.h
#define MX53_PAD_DISP0_DAT13__AUD5_RXFS IOMUX_PAD(0x3C0, 0x94, 3, 0x0, 0, NO_PAD_CTRL)
#define MX53_PAD_DISP0_DAT14__AUD5_RXC IOMUX_PAD(0x3C4, 0x98, 3, 0x0, 0, NO_PAD_CTRL)
#define MX53_PAD_DISP0_DAT16__AUD5_TXC IOMUX_PAD(0x3CC, 0xA0, 3, 0x0, 0, NO_PAD_CTRL)
#define MX53_PAD_DISP0_DAT17__AUD5_TXD IOMUX_PAD(0x3D0, 0xA4, 3, 0x0, 0, NO_PAD_CTRL)
#define MX53_PAD_DISP0_DAT18__AUD5_TXFS IOMUX_PAD(0x3D4, 0xA8, 3, 0x0, 0, NO_PAD_CTRL)
#define MX53_PAD_DISP0_DAT19__AUD5_RXD IOMUX_PAD(0x3D8, 0xAC, 3, 0x0, 0, NO_PAD_CTRL)
3) added this mux configuration into mx53_loco.c -> mx53_loco_pads
As a result :
- I don't have sound from the sgtl5000 (normal because I changed the mux configuration)
- I don't have LCD signal anymore on the corresponding pins(DISP0_DAT[13:19]) of the extension connector (normal because I changed the mux configuration)
- But I don't have I2S signal on these pins :(
4) Then I used IOMux.v2.0.27 to check the iomux configuration, and it said me that there was a conflict because VCC_LCD power rail should be at 3.3v
So I saw that VCC_LCD comes from PMIC DA9053 VLDO4.
I used regulator_set_voltage() then read it again with regulator_get_voltage, I read the good value but physically the voltage didn't change!
Two questions :
- Is it normal that I don't get I2S signals with 2.775V instead of 3.3V or is it an error in my mux configuration?
- How Can I change VLDO4 value?
I think even you keep the VCC_LCD at 2.775V, there should be the I2S signal too. But if you haven't connected any codec on AUD5, you need set the iMX53 as the I2S master to generate the I2S clock. As default in the BSP, the SGTL5000 is the I2S master to generate the I2S clock.
You can check the file "imx-3stack-sgtl5000.c", "#define SGTL5000_SSI_MASTER 1", if you need the iMX53 as the master, you need remove this macro.