5 Replies Latest reply on Mar 19, 2018 6:34 PM by pengfei.zhai_2710136

    Can not establish serial connection with BCM43438 BT

    pengfei.zhai_2710136

      Hi:

           We are developing a WIFI/BLE adapter board based BCM43438 to our RISC-V chip.  The BCM43438 board schematic reference iMX7 development board design and be posted below. After we produced a fully new board, I want use PC to send UART command for test. I first send RESET command (0x01 0x14 0x0C 0x00) to BT with both hardware flow control and without, but none has response. All power are OK, the board use a 26mhz external crystal and a 32.768k LPO. Do I lost some  procedure cause no response?

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        • 1. Re: Can not establish serial connection with BCM43438 BT
          jact

          1. What baud rate are you using?

          2. What tool are you using to send the HCI commands? And have you verified with a logic analyzer that commands are going across properly?

           

          Your HCI reset command is incorrect, although you should still see some response form the chip regardless (error response). The correct sequence is: 01 03 0c 00

           

          In between failed commands, be sure to close the transport, power cycle, and re-open the transport in case you've sent the chip into a bad state.

           

          Jacob

          • 2. Re: Can not establish serial connection with BCM43438 BT
            pengfei.zhai_2710136

            Sorry for a long time to reply..

            1. The uart baud rate is 115200.

            2. I use a USB to Serial Bridge tool (CP2102) to send HCI commands. When I use a oscilloscope to see the signal on uart lines( tx rx cts rts), I find some problems:

                  1/ If only pull up BT_REG_ON pin, the 26Mhz crystal will not output the clock,after pull up WL_REG_ON pin, the crystal works. But as the datasheet said, these two pins are OR relationship, the power will work when either pin is high.
                   2/ The BT uart pins( TX RX CTS RTS) looks has wrong state. If leave the pins dangling, only TX is high, others are low. If connect them to CP2102, the TX RX RTS are high, the CTS is low. So the 43438 chip is actually not ready, because the chip doesn't pull down RTS.

                 Based on the above two points, I guess the part of  Bluetooth circuit does not work, do you have any suggestions?

            Thank you very much for your reply!

            • 3. Re: Can not establish serial connection with BCM43438 BT
              pengfei.zhai_2710136

              In addition, the BT_REG_ON pin can control the power correctly, but only insert this pin the crystal has no output.

              • 4. Re: Can not establish serial connection with BCM43438 BT
                jact

                I'd suggest using the MBT tool to send the HCi commands. Download the SDK and navigate to 43xxx_WiFi/tools/mbt/Release. Refer to the readme for setup details. This will rule out any errors in the way you are sending the HCI commands. The chip should respond to an HCI reset at the very least (prior to patch RAM download).

                 

                Jacob

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                • 5. Re: Can not establish serial connection with BCM43438 BT
                  pengfei.zhai_2710136

                  I have solved this problem whose reason is very simple, the tx and rx pins are connection in wrong way.

                  Thanks very much,

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