TMS320F28377S: USB Boot and VrefHI for ADC

Vidhya Jeyapaul

Part Number: TMS320F28377S
Other Parts Discussed in Thread: C2000WARE, TMDSCNCD28379D, LAUNCHXL-F28379D

Hello Team,

1. Can I use USB pins (130 and 131) of MCU to the USB connector directly for USB device boot mode without FTDI chip? Please clarify.

In F2839D Eval board, USB to UART FTDI chip is used. Dedicated USB pins are not used for boot.

Can you share application circuit of USB Boot option?

2. VrefHI andVrefLO pins.

Aceptable practice is to tie vrefhi to VDDA and Vreflo to VSSA for unused pins.

If I am using all 4 ADC channels (20pins) , how should I connect Vrefhi (A,B,C,D) and Vreflo (A,B,C,D) for external and internal reference modes?

Please clarify,

Kindly Revert.

Thanks,

Vidhya

over 5 years ago

0 Vidhya Jeyapaul over 5 years ago

Intellectual 780 points

++ For2: F28379D Eval board- VrefHI and Lo are connected to precision power supply with opamp. Is opamp needed? Precision 3V supply is for accuracy.

0 Cody Watkins over 5 years ago

TI__Mastermind 42195 points

Vidhya,

There are multiple evaluation boards, some with multiple USB connectors. Please clarify what you are using. Also note that the schematics of all C2000 evaluation boards are located in C2000Ware so this should be easy to determine. C:\ti\c2000\C2000Ware_3_04_00_00\boards
VrefHI questions
1. Internal reference mode is not supported on this device
2. Pin requirements are described in "6.1.` signal descriptions" of the datasheet. https://www.ti.com/lit/gpn/tms320f28377s
3. A good example of how to connect the VREFHI and VREFLO signals can be seen in TMDSCNCD28379D and in LaunchXL-F28379D. The schematics can be found C2000Ware.
4. Yes for good performance a buffer is needed.

Regards,
Cody

0 Vidhya Jeyapaul over 5 years ago in reply to Cody Watkins

Intellectual 780 points

Hello Cody,

For USB: I did find Eval board of F28379D and 77S. Both has SCI boot mode (USB to UART conversion using FTDI chip) option is used.

I am looking for USB boot mode option. Can you please share Eval Board link with USB boot mode option?

For vref: External 3V precision with buffer to be used for VrefHI(A,B,C,D)

Please clarify.

Thanks,

Vidhya

0 Cody Watkins over 5 years ago in reply to Vidhya Jeyapaul

TI__Mastermind 42195 points

Vidhya,

Vidhya Jeyapaul said:
I am looking for USB boot mode option. Can you please share Eval Board link with USB boot mode option?

GPIO 42 and 43 are used for USB bootmode. These pins are connected to J8 of TMDSCNCD28379D.

Vidhya Jeyapaul said:
For vref: External 3V precision with buffer to be used for VrefHI(A,B,C,D)

Please clarify.

I can't tell what you would like clarified. Your statement follows our recommendation. Post with more details on VREF circuit:https://e2e.ti.com/support/microcontrollers/c2000-microcontrollers-group/c2000/f/c2000-microcontrollers-forum/508087/tms320f2837xs-delfino-adc-vref

Regards,
Cody

0 Vidhya Jeyapaul over 5 years ago in reply to Cody Watkins

Intellectual 780 points

Hello Cody,

For USB boot mode , can I directly connect USB pins (GPIO42 and GPIO43) of F28377s MCU to an USB connector?

or Do I need any FTDI chip?

But FTDI converts USB to UART SCI boot mode. Kindly clarify.

Thanks,

Vidhya

+1 Cody Watkins over 5 years ago in reply to Vidhya Jeyapaul

TI__Mastermind 42195 points

A direct connection of GPIO42 and 43 to your USB connector is required to use the USB bootmode. The USB bootmode is using the USB IP on the device to communicate over the USB protocol, please do not confuse this with SCI boot. For SCI boot the FTDI chip is required to convert UART signals to a USB format such that it can communicate to your PC.

Regards,
Cody

0 Vidhya Jeyapaul over 5 years ago in reply to Cody Watkins

Intellectual 780 points

Ok Cody.

Can you please share any supporting circuit reference (USB Connector to MCU pins) for the same? I didn't find it in any EVAL schematics.

Thanks,

VIdhya

0 Cody Watkins over 5 years ago in reply to Vidhya Jeyapaul

TI__Mastermind 42195 points

Vidhya,

Where were you looking for schematics?

Cody Watkins said:
schematics of all C2000 evaluation boards are located in C2000Ware so this should be easy to determine. C:\ti\c2000\C2000Ware_3_04_00_00\boards

Specifically for TMDSCNCD28379D:

C:\ti\c2000\C2000Ware_3_04_00_00\boards\controlCARDs\TMDSCNCD28379D

Best of luck,
Cody

0 Vidhya Jeyapaul over 5 years ago in reply to Cody Watkins

Intellectual 780 points

Thanks Cody

0 Vidhya Jeyapaul over 5 years ago in reply to Vidhya Jeyapaul

Intellectual 780 points

Hi Cody,

C2000 device can act as host/device.

Micro USB port will be connected to a PC (GUI) for USB boot mode.

so Vbus will be self powered and only monitoring should be done at C2000 using a GPIO pin and no need to source Vbus separately from controller board?

Please clarify.

Thanks,

Vidhya

0 Cody Watkins over 5 years ago in reply to Vidhya Jeyapaul

TI__Mastermind 42195 points

Vidhya, that's a design choice. If you look at the contorlCARD schematic you'll see that the ability to drive Vbus on the micro USB connector is controlled by a GPIO.

If your connecting to a PC typically the PC will provide Vbus, so there is no need.

Regards,
Cody

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TMS320F28377S: USB Boot and VrefHI for ADC