IOMux_TOOL 3.4.0.3, power fields CSI_REXT DSI_REXT

[danielmachaty]

Hello.

I'm designing processor module with iMX6DQ and I'm using IOMUX_TOOL v3.4.0.3 to assign GPIOs. What is the required level in Power tab for fields CSI_REXT and DSI_REXT? No voltage level mentioned in datasheets. Also these fields have not been present in previous versions.

Thank you.

Daniel Machaty

[igorpadykov · Accepted solution]

Hi Daniel

power for CSI_REXT and DSI_REXT is NVCC_MIPI for both,

this is depicted on p.3 SPF-27392 i.MX6_SABRE_SDP_DESIGNFILES

These are special signals, not GPIOs and not muxed with other signals.

They are used for connection with external resistors, providing biasing

for MIPI analog circuits.

Best regards

igor

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[danielmachaty]

Hello Igor,

thank you for the answer.

I am aware, that this signal belongs to NVCC_MIPI power domain and I am quite familiar with it's function.

But I am not sure if the CSI_REXT/DSI_REXT output voltage value is same as the NVCC_MIPI power domain supply voltage (i.e. 2.5V according to IMX6DQ6SDLHDG hardware design guide, p. 71). And if it is, then I have no idea why this field is separate from NVCC_MIPI voltage field and why these fileds were added in the new version of IOMUX tool. I suppose there was a reason for this?

Thank you,

Best regards,

Daniel Machaty

[igorpadykov]

Hi Daniel

these signals do not provide voltage.

They are routed for connection to precise resistors,

so precise reference current is provided to MIPI circuits.

I do not think that there is special reason behind this

in new version of IOMUX tool, probably this was added just

for completeness, so all pins have the same universal description.

Best regards

igor

[danielmachaty]

Hello Igor,

well, this becomes a little philosophic discussion, but the reference current is obtained by providing reference voltage to a reference resistor, therefore a voltage is provided by this pin. If it's not, then there is no reference current :-)

I am still curious why these fields are included in section with header "Assign voltage levels to power pins". This has to be a mistake, not "added just for completeness". And if user is supposed to enter some power rail value, it should be mentioned in documentation..

Best regards,

Daniel Machaty

[igorpadykov]

Hi Daniel

resistors values are strictly defined in IMX6DQ6SDLHDG

Table 2-13. Reference resistor recommendations

there is no freedom to change smth.

Best regards

igor

[danielmachaty]

Hello Igor,

Please note, that I didn't say a word about changing resistance value.

"if user is supposed to enter some power rail value" doesn't mean changing resistance. It means changing the voltage level in the field CSI_REXT / DSI_REXT, which is by default "0.000". If I am supposed to enter a value (voltage level value), then there should be a voltage level specification for CSI_REXT / DSI_REXT pins somewhere. And yes, I insist on the fact that I have a freedom to change the value in this field :-)

Best regards,

Daniel Machaty