Can I have the schematic of CP2105 (USB to UART)?

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Anonymous
Not applicable

Hello,

    I have designed a board with BCM20737S and few sensors (max 3.3V). Now I am designing a separate board for the USB to UART to burn the firmware and also for the debug trace.

1. May I know if I can use just the pins 12 and 13 for TX RX connections to BCM20737S and leave pin 20 and 21 open.

2. Can I use a switch at the TXD_ECI to BCM20737S RX interface to toggle between burning firmware mode and debug mode?

Thank you,

Tejas

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1 Solution
JacobT_81
Employee
Employee
250 replies posted 100 replies posted 50 replies posted

Hi tejas​,

The cable that mwf_mmfae​ linked will be sufficient for most things you'll be doing. It's a much faster and cheaper than building your own.

In response to your first two questions:

1. May I know if I can use just the pins 12 and 13 for TX RX connections to BCM20737S and leave pin 20 and 21 open.

          Yes. 20 and 21 are only used for PUART. Unless you want your traces routed through PUART or you plan to communicate to the board over PUART in some fashion, you don't need these.

2. Can I use a switch at the TXD_ECI to BCM20737S RX interface to toggle between burning firmware mode and debug mode?

          Yes. You need only a single switch on the TXD_ECI line to switch between debug and download mode. Reset with the switch connected to download, reset with it off to be able to see traces come through the UART.

Jacob

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4 Replies
MichaelF_56
Moderator
Moderator
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Have you looked at using one of the USB to Serial cables from FTDI? This will be alot more straight forward.

I believe the correct model is FTDI TTL-232RG-VREG3V3-WE - you MUST get the 3V output.

http://www.ftdichip.com/Products/Cables/USBTTLSerial.htm

Anonymous
Not applicable

Thank you for the link. May I know if I have to make any changes to use UART debug trace?

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JacobT_81
Employee
Employee
250 replies posted 100 replies posted 50 replies posted

Hi tejas​,

The cable that mwf_mmfae​ linked will be sufficient for most things you'll be doing. It's a much faster and cheaper than building your own.

In response to your first two questions:

1. May I know if I can use just the pins 12 and 13 for TX RX connections to BCM20737S and leave pin 20 and 21 open.

          Yes. 20 and 21 are only used for PUART. Unless you want your traces routed through PUART or you plan to communicate to the board over PUART in some fashion, you don't need these.

2. Can I use a switch at the TXD_ECI to BCM20737S RX interface to toggle between burning firmware mode and debug mode?

          Yes. You need only a single switch on the TXD_ECI line to switch between debug and download mode. Reset with the switch connected to download, reset with it off to be able to see traces come through the UART.

Jacob

Anonymous
Not applicable

Thank you for the reply. Really appreciate that

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