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FAQ

This list might help you resolve some issues.

I received an error

Description of all return values is in the libtropic_common.h (lt_ret_t enum). However, some errors may have a seemingly unrelated cause; see the following paragraphs.

LT_L1_CHIP_BUSY

Normally, this means that the chip is busy processing an operation and is unable to respond. However, it can also mean that the SPI lines (mainly MISO) are tied to ground (causing the host to receive all zeroes). Check your connections.

The reason is that we detect the status of the TROPIC01 using a single flag; if all data are zero, we cannot distinguish between the TROPIC01 being truly busy and the host receiving only zeroes.

LT_L1_CHIP_ALARM_MODE

Normally, this means the TROPIC01 entered Alarm Mode. However, it can also mean — similarly to LT_L1_CHIP_BUSY — that all ones are received on MISO. Check your connections.

LT_L3_DATA_LEN_ERROR

This error normally means that the L3 packet size we sent to the TROPIC01 is incorrect, which can be caused by a bug or an attack. However, it can also mean that the chip select is connected incorrectly. Check your connections and GPIO assignments.

Chip Select Handling

We use a GPIO to handle chip select, not the SPI peripheral's native chip select output.

LT_L3_INVALID_CMD or LT_L2_UNKNOWN_REQ

This error means that the TROPIC01 does not recognize the L3 command or L2 request it received. However, this behavior can be caused by the TROPIC01 being in Maintenance Mode. Maintenance Mode does not implement the entire API — it does not implement Handshake_Req nor any L3 commands, so handshake attempts will always fail.

A TROPIC01 will be in Maintenance Mode after a user-triggered reboot (calling lt_reboot with TR01_MAINTENANCE_REBOOT as startup_id). In that case, reboot the chip back to Application Mode by calling lt_reboot with TR01_REBOOT. During evaluation you can also use the lt_ex_show_chip_id_and_fwver.c example, which reboots to Application Mode at the end.

However, a TROPIC01 can also enter Maintenance Mode automatically after an unsuccessful update or if firmware banks are empty or corrupted. In that case, a simple reboot will not help; you must run the firmware update again, either using the lt_ex_fw_update.c example or from your application code.

I cannot establish a Secure Session

There are two main causes:

  1. You are using incorrect pairing keys. All new TROPIC01s use production pairing keys, which are used by default in Libtropic. Some devkits still contain preview chips (engineering samples). For those, you need to use different keys. Refer to the Default Pairing Keys for a Secure Channel Handshake.

  2. Your TROPIC01 is in Maintenance Mode. Reboot to Application Mode by calling lt_reboot with TR01_REBOOT, or during evaluation use the lt_ex_show_chip_id_and_fwver.c example, which reboots to Application Mode at the end.

FW update failed

If our lt_ex_fw_update example program failed:

  1. Try the suggestions in I received an error.
  2. Make sure you have correct values set in the following CMake options:
  3. Make sure you are not attempting a firmware downgrade — TROPIC01 does not allow this.

What is the part number (P/N) of my TROPIC01?

You have two options:

  1. Read it from the packaging you received your TROPIC01 product in.
  2. Run our example program lt_ex_show_chip_id_and_fwver, which does not require the Secure Channel Session. For building instructions, refer to our Integration Examples.

What is the silicon revision of my TROPIC01?

You have two options:

  1. Read the product number (P/N) from the packaging you received your TROPIC01 product in. After that, refer to the Available Parts section (in the TROPIC01 GitHub repository) and read the linked Catalog list, which will help you decode the silicon revision based on your P/N.
  2. Run our example program lt_ex_show_chip_id_and_fwver, which does not require the Secure Channel Session. For building instructions, refer to our Integration Examples.

What FW versions is my TROPIC01 running?

Run our example program lt_ex_show_chip_id_and_fwver, which does not require the Secure Channel Session. For building instructions, refer to our Integration Examples.