I'm interfacing an eMMC chip to the i.MXRT1062 controller using USDHC2 peripheral. For the eMMC to support HS200 mode the VDDQ Voltage(I/O Voltage) of eMMC need to be between 1.7V–1.95V i.e 1.8V.
I can change the NVCC_SD1 voltage to 1.8V and can get away with it, but it looks like the CSX,1 pin from SEMC also uses this voltage group(The rest of SEMC pins uses 3.3V).
There is no other option available for me to change the MUXing of CSX,1 or use any other CSX as all other pins have been consumed.
So my questions are,
1. Why isn't the tool generating a warning when the SEMC is using 2 different voltages?
2. Is there any way out? apart from using a hardware voltage level converter at CSX,1 to make it 3.3V compatible
Thanks for your reply.
First things first, I have already configured the power groups as bellow.
Secondly, all the pins from SEMC peripheral (apart from CSX,1) use NVCC_EMC power rail which is at 3V3.
Now for CSX,1 I have 2 options as you said:
1. Use L4 pin, GPIO_SD_B1_07, powered by NVCC_SD1
2. Use D7 pin, GPIO_B0_00, powered by NVCC_GPIO
But I can't go with either option as pin L4 which is using NVCC_SD1 power rail is at 1V8 and pin D7(NVCC_GPIO-3v3) is already been used for ENET2_MDC and I can't change the muxing of ENET2_MDC as the other optional pin is already used for another purpose.
So the question remains,
1. Even after having the power group defined, why didn't the tool generated a power group conflict warning?
2. Can we stick to the same pin(L4, NVCC_SD1-1V8) and use an external hardware voltage level conversion circuit to switch the 1V8 signal to 3V3 as the CSX, 1 is only output signal? and how common is this approach? do you see any downside of it or foresee any problem?
The SEMC_CSX,1 as GPIO_SD_B1_07 is powered by NVCC_SD1 - that is,
the same voltage is used as for the rest uSDHC2 signals (SD_B1 group), therefore
there is no voltage conflict here. Generally it is possible to use voltage convertor for
the output SEMC_CSX,1 signal.
It is possible to use different pin mux-ing options for the pins in order to avoid
conflicts. For example SEMC CSX1 has two options:
L4 pin, GPIO_SD_B1_07, powered by NVCC_SD1
D7 pin, GPIO_B0_00, powered by NVCC_GPIO
Note, in order to get warnings regarding power voltages conflicts - it is needed to
setup power supply voltages (in Power Groups tab of the i.MX Pins tool).
Have a great day,
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