ST25RU3993 HPEV UART Comminication between STM MCU and Host

SPraj.1 · ‎2021-04-05

I have development board of ST25RU3993 HPEV. I am testing TAG detection uising GUI application -provided by STM.

As this application works using USB interface between STM MCU and HOST. Instead of USB interface I want to check UART communication with HOST.

Can you plese ket us know how can i check UART communication and where to take wires and what changes are required in hardware.

Also I need some informatrion of protocol because we need to develop a application on UART to read tag information

SPraj.1 · ‎2021-04-07

After connection to J7 RX and TX. Samle firmware 2.3.0.0 will work or do I need to change any thing in firmware. Everybody is saying different method. Please confirm me exact method to bypass onboard Ft231 and use j7 rx tx to connect Host. And for this what hardware and software changes are required.

Nick K · ‎2021-04-07

Hello SPraj.1

as described already by Bart, yes please put the FT231 IC (U13) into reset state to avoid crosstalk.

power the board with the additional power supply for proper supply.

you need to control the RTS and DTR lines, as described above, otherwise the STM32L4 FW will not boot at all.

if you only want to bypass the FT231 IC no FW changes are needed, stock FW works.

SPraj.1 · ‎2021-04-07

Hello Nick,

As you said I have put U13 in reset state and connect J7 RX/TX to pc through CP2102(USB UART bridge) and run Reader Suite application. Application ask me to update firmware and when i try to update firmware it gives device is not recognised error.What is the reason of this reason?

Nick K · ‎2021-04-08

Hello SPraj.1,

can you confirm that CP2102 use the same voltage level as STM32L4 ? 3.3V ?
can you confirm that the CP2102 is able to operate at 3MBit/sec ?
just to be sure, did you also connected DTR/RTS lines between the HPEV and the CP2102 ? as explained, they are needed to bring the STM32L4 into bootloader mode, if you want to upgrade the FW. DTR/RTS lines are also used by the GUI during connect and when starting the upgrade process. If DTR and RTS are not proper configured the board will not boot from User code nor enter bootloader.
just to be sure, do you have connected GND ?
have you cross connected the Tx (board) with Rx (CP2102) or how is your CP2102 labeled ? does the CP2102 required Tx to Tx connect or Tx to Rx ?
could you send a picture with your wiring between the board and the CP2102 ?
could you send traces of the DTR, RTS, Rx, Tx lines when trying to connect the GUI with the board ?

SPraj.1 · ‎2021-04-08

can you confirm that CP2102 use the same voltage level as STM32L4 ? 3.3V ? - Yes it uses same 3.3V

can you confirm that the CP2102 is able to operate at 3MBit/sec ? - No it is operatable upto 1Mbit/sec

just to be sure, did you also connected DTR/RTS lines between the HPEV and the CP2102 ? as explained, they are needed to bring the STM32L4 into bootloader mode, if you want to upgrade the FW. DTR/RTS lines are also used by the GUI during connect and when starting the upgrade process. If DTR and RTS are not proper configured the board will not boot from User code nor enter bootloader. - No RTS and DTR lines are not connected between CP2102 and STM32l4. Already latest firmware is downloaded previously then also it asks for firmware upgrade while UART is connected.

just to be sure, do you have connected GND ? - YES

have you cross connected the Tx (board) with Rx (CP2102) or how is your CP2102 labeled ? does the CP2102 required Tx to Tx connect or Tx to Rx ? - It is cross connect I have verified that with other board. Its Tx pin connected to RX to STM32L4.

could you send a picture with your wiring between the board and the CP2102 ? - Images are attached.

could you send traces of the DTR, RTS, Rx, Tx lines when trying to connect the GUI with the board ? - Did not get your question. what you want waveforms?

Nick K · ‎2021-04-08

Hello SPraj1.

can you confirm that the CP2102 is able to operate at 3MBit/sec ? - No it is operatable upto 1Mbit/sec
- The stock FW operates at 3Mbit/sec. If CP2102 operates with max 1Mbit/sec communication can not work. Please use a USB-UART converted which is able to work with 3Mbit/sec.

just to be sure, did you also connected DTR/RTS lines between the HPEV and the CP2102 ? as explained, they are needed to bring the STM32L4 into bootloader mode, if you want to upgrade the FW. DTR/RTS lines are also used by the GUI during connect and when starting the upgrade process. If DTR and RTS are not proper configured the board will not boot from User code nor enter bootloader. - No RTS and DTR lines are not connected between CP2102 and STM32l4. Already latest firmware is downloaded previously then also it asks for firmware upgrade while UART is connected.
- RTS and DTR lines are needed to define boot-behavior of the STM32L4. If DTR and RST are not configured correct the board will not boot. Neither into bootloader code nor into user code. Please connect them as the GUI controls them to boot the board.

could you send a picture with your wiring between the board and the CP2102 ? - Images are attached.
- Thanks for the picture, but the connections on the CP2102 side is not visible, the cable for GND connection is not visible and the DTR, RTS pins are not connected.

could you send traces of the DTR, RTS, Rx, Tx lines when trying to connect the GUI with the board ? - Did not get your question. what you want waveforms?
- Yes, waveform captured at the DTR, RTS, Rx, Tx wires to check the communication on the wires, if it can be assumed that all wires are connected correct and communication still not work

SPraj.1 · ‎2021-04-08

Point#1: Currently we are not having UAB-UART bridge that support 3 Mbit/sec. So I will order it but till now What if I change the firmware baud rate to lower? in our final application STM32L4 will connect to BLE thorugh and UART and it receives command so we need to change the baud rate. So is it good to change the baudrate?

Point#2: You mean to say that RTS and DTR lines are connected to CP2102? If it is connected to CP2102 then how it can be configured by GUI application?

Point#3: GND is connedcted to another side of board so it is not visible. BLUE - Tx, GREEN - RX and BLACK -GND.

Point#4: Give me some I will ask my hardware engineer to capture the waveforms and send it to you.

SPraj.1 · ‎2021-04-08

Hello Nick,

As ou said we have changed the USB UART converter and connect RTS and DTR. But still we are getting same result. I am attaching all the images for your reference.

SPraj.1 · ‎2021-04-08

Hello @Nick K

We have also captured DTR and RTS Signals. Please find attached images. Still same result device is not recognised.

Nick K · ‎2021-06-28

Hello,

let me summarize, based on the discussion, how to replace the ST25RU3993 EVAL/HPEV onboard FT231 IC

Unsolder U13 or put U13 (onboard FT231) into reset mode by remove R6 and short C33
Connect your own USB-UART converter at J7 by using RX, TX, DTR and RTS pins.
IMPORTANT: To avoid FW changes a USB-UART convert IC supporting 3MB is required.
IMPORTANT: DTR and RTS pins are used to control RST and BOOT0 pins of onboard STM32L4 and needed for proper board booting
Use ST25RU3993 Reader Suite GUI and connect to the board through your own UART-USB converter
Alternative: Develop your own UHF Host application. For this it is recommended to have a look at the STUHFL_demo source code example and follow the connection procedure.
- Connect to COMxx with 8N1 and 3MBit/sec
- set DTR high, to force STM32L4 start from user code
- toggle RTS (high -> low), to restart the board
- Wait ~400ms to give board time to boot

BR