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MSP430F5659: MSP430 USB BSL invoke

Part Number: MSP430F5659

Hi Team,

We are working on a custom board (second revision) with MSP430F5659. As per the flowchart in page 3 of  slaa452c.pdf, when PUR pin it pulled high when Reset is pressed with the presence of VBUS, USB BSL is invoked.

But, we are seeing some different scenario in USB BSL invoke:

Case 1:  By default, VBUS will not be available. VBUS is controlled through a switch, VBUS is available after 500ms of Reset is held low and Rest is released after 500ms. We have a 120E pull-up resistor at PUR pin to VUSB. In this case, USB is not getting recognized at the Host. 

We also tried by connecting the device to Windows PC. The USB cable is plugged to PC while the reset switch is pressed. Still USB is not getting recognized at the Host. 

Case 2: When the USB is getting enumerated, when we press the Reset switch, USB is still enumerated and once we release the switch, USB gets disconnected and USB is not getting recognized at Device Manager.

Case 3: We are controlling the BSL sequence from the Host processor. PUR pin is controlled by the GPIO of Host Processor present in separate board. In this case, there is no external PUR pull-up resistor present on the board. This GPIO signals travel from the Host Processor to MSP430 via a cable assembly of length 200mm. Hence, we have a ESD component TPD6E05U06RVZ near the MSP430 end.Even if the PUR is pulled up by the GPIO of Host Processor, USB is not recognized. We tried after removing the ESD component and disconnected the Cable then tried the Case 4 below. 

Case 4:  When VBUS 5V is made available in default and USB cable is connected to Windows PC even without pressing  reset, USB is getting enumerated even without PUR pulled High externally. MSP430 is powered from 3V3 LDO and 5V is provided from switcher on board, both powered from external 12V supply. There is approximately 750ms delay between 3V3 generation and 5V generation. As per the recommendations, we have 2M weak pull down at PUR pin and when probed, PUR pin detected to be low. I am not sure how the USB is getting detected in this case.

Are we missing anything here? Have anyone faced similar issue and please let us know to fix this issue.

What modification to the circuit do you suggest?

  • Hello,

    Can you verify that your USB and BSL hardware have been designed correctly?  A great reference for starting a USB Design from scratch is provided in Figure 8 of document SLAA457b.pdf. 

    If USB and BSL have been designed correctly, then holding down the 'BSL' button/switch  while connecting the device side USB cable (not JTAG cable) should place your device in 'BSL' mode.    I think you stated that you are pressing the 'Reset' button.  The Reset button resets the entire board and is usually not setup to place your device in 'BSL' mode.

    Regards,

    Arthi

  • Hi,

    Thanks for your reply.

    We don't have any switch for BSL. We have switch only for Reset. As soon as a BOR occurs, the PUR pin is the first thing that is checked.

    1. When we are  flashing from Windows PC, we will add 100E pull-up at PUR pin to VUSB. There will not be any supply to VBUS. We need to press the reset Button while inserting the USB cable. VBUS will be powered through the USB cable from PC and VUSB will be generated by internal LDOs. And PUR pin will be pulled high once PUR is generated.

    But, in our case if we are not connecting the USB cable without pressing the reset button , USB enumeration is happening if there is no PUR pull-up to VUSB. But with presence of PUR pull-up, USB is not getting detected.

    Our main Concern is that the USB is not enumerated if we have Pull-Up at PUR.

    2. There is some difference in PUR and D+ connection between our design and reference design in Figure 8 of document SLAA457b.pdf

    In Figure 8 of document SLAA457b.pdf, D+ line has 1.4K pull-up to PUR and PUR pin has Pull-up to VUSB.

    In our design, we have provided an 1.5K pull-up to VBUS at D+ line and there is no pull-up from D+ to PUR.

    But I am not sure how will this impact placing the device in BSL.

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