EK-TM4C123GXL: TivaC launchpad USB connection and powering questions. Thanks!

Hi Jackie,
I'm not familiar with AFE4490SPO2EVM so can't answer much about it. The TM4C123 MCU can act as an USB host. Please see the user guide at www.ti.com/.../spmu296.pdf. Depending on how much of the current is needed by the external USB device you may power the LaunchPad and external USB device via the debug USB port. Also check this post for additional info. e2e.ti.com/.../1278330

Jackie Jackie said:

trying to connect Arm TivaC LaunchPad with connect AFE4490SPO2EVM  via USB port, to get the data acquired.

and later:

Jackie Jackie said:

Waiting for reply since we need to determine the solution and purchase the product now.

Does not your 2nd quote,  "need to determine - then (maybe) purchase" run counter to your first, "trying to connect?"     Does not "trying to" suggest an "active approach" in which both hardware & software are employed?    Yet quote 2 suggests your "trying" is "theoretical only" (and not at all described.)

There is no mention of any specification for (either) data accuracy or rate - usually (some) specification is "in play" - minus that info it is not possible to respond w/focused assurance...    There must have been "good consideration" for the choice of your external device - yet w/such explanation held "silent" - it (again) confounds "serious" tech response...

Hi Charles,

Thanks for the reply.

Just further confirm the option you mentioned:

to power the launch pad, I can connect PC with launch pad via the debug USB

at the same time, connect the launch pad (host mode) with another USB device, via another USB interface (left side)

is this correct? since two USB interfaces on the launchpad are both used, one for powering (debug USB), and another for communication (device USB port)?

Could you check the feasibility? Thanks!

Jackie

Hi Jackie,

 You will need to populate the R25 and R29 with the 0ohm resistors. Please find out if your device can be self-powered. If you need the host to provide the power then please refer to the below about the USB connectivity in the LaunchPad user guide.

The TM4C123GH6PM target device is also capable of USB embedded host and on-the-go (OTG)

functions. OTG functionality can be enabled by populating R25 and R29 with 0-Ω resistors. These

resistors connect the USB ID and USB VBUS signals to PB0 and PB1. When these resistors are populated,

PB0 and PB1 must remain in the respective USB pin mode configurations to prevent device damage. PB0

and PB1 are also present on the J1 BoosterPack header. Therefore, if R25 or R29 are populated, care

must be taken not to conflict these signals with BoosterPack signals.

USB embedded host operation can be enabled in the same way for USB devices that are self-powered.

Providing power when acting as a USB host requires a BoosterPack with power switching and appropriate

connectors. All USB host signals are available on the BoosterPack interface except D+ and D–, which are

only available on the USB micro-A/-B connector and the two adjacent test points.

Please also refer to the below post if you want to use the debug USB to provide power to your device USB acting as a host.

e2e.ti.com/.../1278164

Hi Charles,

Great, this really helps a lot.

Just have questions about the details of the OTG/host function, as follows:

1. In OTG mode, populating R25, R29 (zero ohm), will connect USB ID/Vbus to PB0/PB1 of the MCU pins.
But what does 'PB0 and PB1 must remain in the respective USB pin mode configurations to prevent device damage' mean?

2. In host mode, does 'USB embedded host operation can be enabled in the same way for USB devices that are self-powered' mean: populating R25/29 too?

3. In host mode, 'Providing power when acting as a USB host requires a BoosterPack with power switching and appropriate connectors', what does this mean?

In the following post you shared with me, the USB host can either get power from the debug USB cable ( connect H18 to H19), or on its pin (connect an external 5V power supply ). What is different between these solutions and the 'BoosterPack with power switching and appropriate connectors'?

e2e.ti.com/.../1278164

Very detailed questions, but approaching the final solution I feel.

Thank you very much for your time!

Best
Jackie

Jackie Jackie said:

1. In OTG mode, populating R25, R29 (zero ohm), will connect USB ID/Vbus to PB0/PB1 of the MCU pins.
But what does 'PB0 and PB1 must remain in the respective USB pin mode configurations to prevent device damage' mean?

It means to caution users that if you re-purpose PB0 and PB1 for non-USB functions then you can create drive conflict with other drivers driving these pins. Just don't use PB0/PB1 for non-USB functions.

Jackie Jackie said:

2. In host mode, does 'USB embedded host operation can be enabled in the same way for USB devices that are self-powered' mean: populating R25/29 too?

If your external USB device is self-powered then you don't need to populate the R25/29.

Jackie Jackie said:

3. In host mode, 'Providing power when acting as a USB host requires a BoosterPack with power switching and appropriate connectors', what does this mean?

If you want to supply power to your external USB device then you need to give the 5V via the VBUS pin on the J3 connector. If your external device does not consume a lot of current that you may use the Debug USB power to supply to the Device USB.