QTFM Gen-2 Sensor Firmware Update Guide

Important: the Updater’s baud rate must match the sensor’s baud rate

The single most common failure mode when updating sensor firmware is a baud rate mismatch between the sensor and the QTFM2 Firmware Updater. The Updater talks to the sensor over UART, and if the two are not on the same baud rate every byte gets garbled. The bootloader handshake fails silently, and the erase step then reports an Expected ACK (0xCC), got 0xF3 error.

Before you start the update:

1. Note the sensor’s current baud rate. Open the QTFM2 UI, look at the Connection panel, and write down the baud rate you connected at. Sensors that have been running with a Magpie are almost always at 921600; bare sensors out of the box may be at 115200.
2. Set the QTFM2 Firmware Updater’s Baud dropdown to that same value when you reach the Updater connection step below. V1.1 of the Updater supports up to 921600 baud, so for most users this just means selecting 921600 in the dropdown.

If you see No ack (proceeding anyway) or Expected ACK (0xCC), got 0xF3 in the Updater console, that is the baud-mismatch signature. See the Troubleshooting section for the fix.

Important: put the sensor in idle mode before flashing

Flashing while the sensor is in autostart, locking, or actively measuring can cause the bootloader handshake to drop partway through the flash and leave the sensor in an unresponsive (“bricked”) state. Idle the sensor before clicking Program Firmware.

Two ways to do it:

• From the Updater: after you Connect, click the Disable auto-start mode button next to the Connect button. This is the easiest option and is built into the Updater for exactly this purpose.
• From a terminal: send ~Stop~ over the sensor’s serial interface before launching the Updater. ~Stop~ halts any autostart / LI_Set / Reop / Warmup activity that’s currently in progress. (Requires sensor firmware V1_44 or newer.)

If a flash does hang partway and the sensor becomes unresponsive afterward, the Updater includes an Unbrick ECU recovery option — see the Troubleshooting section.

Which connection path?

The Updater itself is the same in both cases. The only difference is how you physically connect the QuSpin Standard Comms board to the sensor.

Downloads

You need two files: the QTFM2 Firmware Updater (the Windows tool) and the encrypted firmware image for your sensor.

The Updater (Windows)

The firmware image

What’s new in V1_44

• Reliability fixes (2026-07-08 build). Faster automatic recovery from IMU read stalls with clearer status messages, stricter internal checks on direct settings writes (out-of-range addresses are now rejected with an error instead of being silently misapplied), and a fix that prevents a firmware update from unintentionally changing a saved vector timing setting.
• Custom user-saveable profile slots. Save up to three sensor configurations to EEPROM with ~SaveSlot1~ / ~SaveSlot2~ / ~SaveSlot3~, switch between them with ~LoadSlotN~, and list with ~ListSlots~. See the Sensor Profile Configuration Guide for the full workflow.
• Sensor-Only GPS Sync. The sensor now accepts the 11-byte UTC frame on its main UART, so non-Magpie hosts can drive GPS sync directly. See Method 4 in the Sync Guide.
• Integrator workflow tilde commands. ~Stop~ to halt autostart / LI_Set / Reop / Warmup, ~apply~ to re-read EEPROM without rebooting, ~Warmup~ background pre-warmup, ~ADDR,VAL~ direct EEPROM write, and ~report~ to dump 28 key settings. These tilde commands bypass the ASCII command-lock so a locked sensor can still be reconfigured by an integrator host.
• Better cold and hot laser autostart. Wait_for_PD_signal() recovery loop rewritten with a trend-based heat/cool decision, wider entry condition, and a real heater escalation. Addresses the multi-restart symptom seen at sub-zero ambient and the lock-SP clobber seen at moderately cold ambient.
• Watchdog tuned to thermal physics. Reload budget raised from 15 s to 50 s so legitimate long laser/cell autostart states do not trip spurious resets. Real hangs still recover in approximately 50–100 s.
• Boot-banner diagnostics. #Reset cause (RESC): 0xN now prints on every boot for unambiguous reset-source attribution (POR / brownout / WDT / SW). Sync-mode display on the boot banner fixed, and the _A / _B suffix on the #FPGA: line restored.
• PPS realign hardening. Extended ISR_ERROR soak window after a PPS realign suppresses the spurious #ISR.Er4 burst. The @NNN sample counter now stays continuous across realigns so multi-sensor data streams stay aligned.

Update procedure

These steps apply to both Path A (sensor inside a Magpie, via the MiniACB flex connector) and Path B (bare sensor, direct connection). The only difference is where the Standard Comms board plugs in.

Before you start

• QTFM2 Firmware Updater V1.1 downloaded to your PC (from the Downloads section above)
• The encrypted firmware image (.bin.enc) downloaded to your PC (also from the Downloads section)
• QuSpin Standard Comms board and a USB cable (data cable, not charge-only)
• The sensor powered, connected, and confirmed working in the QTFM2 UI before you start — this is also how you confirm the current baud rate

Steps

1. 1 Connect the Standard Comms board.
   Path A (sensor inside a Magpie): Remove the outer Magpie shell to expose the flex connector on the side of the MiniACB board (highlighted below), then plug the Standard Comms board into that connector. The sensor stays mounted in the Magpie sled — no need to disconnect or unmount it.

Path B (bare sensor): Connect the Standard Comms board directly to the sensor’s flex cable, as shown below.

Plug the Comms board into a USB port on your PC. Windows should assign it a COM port number.

1. 2 Identify and configure the COM port. Open Device Manager (search “device manager” in the Windows search bar) and expand Ports (COM & LPT). With the Standard Comms board plugged in, a new COMN entry appears in the list — that entry is your sensor. Note the number; you’ll select it in the Updater at step 7.
   Recommended: right-click that COM port → Properties → Port Settings → Advanced and set Latency Timer (msec) to 1 (the Windows default is 16) for the fastest data transfer to the PC. This matters most for live streaming in the QTFM2 UI rather than for the flash itself, but it is convenient to set now while you are in Device Manager.

1. 3 Confirm the sensor’s current baud rate. Open the QTFM2 UI, connect to the sensor on the COM port you just got, and confirm the baud rate that lets you connect cleanly. Write that number down; you’ll need it in step 6. If the sensor was previously connected to a Magpie, it is almost certainly at 921600. Bare sensors out of the box are usually at 115200.
2. 4 Close the QTFM2 UI completely. The Updater needs exclusive access to the COM port. If the QTFM2 UI is still holding the port open in the background, the bootloader handshake will fail even when the baud rate is correct. Close any other application that might have the same COM port open (PuTTY, Arduino Serial Monitor, etc.).
3. 5 Launch the QTFM2 Firmware Updater. Run QTFM2_Firmware_Updater_V1_1.exe from the location where you saved it.

1. 6 Select the COM port and matching baud rate. In the Connection panel, set Port to the COM port for the Standard Comms board and set Baud to the value you wrote down in step 3 (for most users this is 921600). Click Connect. You should see a clean Connected to COMN at BAUD line in the console with no garbage characters following it. Garbage characters indicate the baud rate is wrong — go back to step 3.
2. 7 Browse to the firmware image. In the Firmware panel, click Browse and select the .bin.enc file QuSpin sent you.
3. 8 Click Program Firmware. The Updater will decrypt the .bin.enc file, send the bootloader entry sequence to the sensor, erase the existing firmware, flash the new image, then verify and report success. The progress bar in the Updater shows the flash progress. Total time is typically 30 to 60 seconds.
4. 9 Power-cycle the sensor and confirm the update. Disconnect the sensor power, wait a few seconds, and reconnect. Open the QTFM2 UI, connect at the same baud rate as before, and look at the boot banner for the new firmware version line. If the version line shows the version you flashed, you’re done.

#Firmware_Version uC:T2M0_YYYY_M_DD:V1_NN_EENN

Troubleshooting

Updater console shows Expected ACK (0xCC), got 0xF3 (or similar non-0xCC byte)

This is the signature of a baud rate mismatch between the sensor and the Updater. The line just above it — No ack (proceeding anyway) — is the real failure point: the Updater sent the bootloader ping and never got the expected 0xCC response, because the bytes were garbled in transit. The erase command that follows then reports back whatever the running sensor firmware happened to spit out as it tried to parse the bootloader bytes as ordinary commands.

Fix:

1. Open the QTFM2 UI and confirm the baud rate the sensor is actually at (it should connect cleanly with no garbage characters in the terminal at that baud).
2. Close the QTFM2 UI completely.
3. Re-launch the QTFM2 Firmware Updater, set the Baud dropdown to that same value, and Connect / Program Firmware again.

Updater shows garbage characters at the moment it connects

Same root cause as above — the baud rate is wrong. Garbage characters appearing in the console right after the Connected to COMN line means the sensor was emitting bytes (a boot banner, status line, etc.) at one baud while the Updater was reading them at another. Match the baud and reconnect.

Updater says it can’t open the COM port

Another application is holding the COM port open. Common culprits: the QTFM2 UI, PuTTY, the Arduino IDE’s Serial Monitor, or a previous Updater instance that didn’t fully release the port. Close all of them and try again. If the port still won’t open, unplug and replug the Standard Comms board to reset the USB connection.

USB port issues

A small number of users have hit framing errors on USB 3 ports that did not reproduce on USB 2. If the baud rate is correct, the QTFM2 UI is closed, and the handshake still fails, try a different USB port on your PC — preferably a USB 2 port if one is available.

The flash stopped partway through and now the sensor is unresponsive (“bricked”)

If the flash hangs or times out partway (for example, “stuck at 24%”) and the sensor stops responding to subsequent connect attempts, the Updater includes an Unbrick ECU recovery option for exactly this case. The Unbrick ECU checkbox sits between the Connect button and the progress bar. Check it when a normal Connect + Program Firmware run fails to recover an unresponsive sensor.

Recovery procedure:

1. Close any other application that has the COM port open (QTFM2 UI, terminals, etc.).
2. Re-launch the QTFM2 Firmware Updater and select the sensor’s COM port and baud rate.
3. Check the Unbrick ECU (check this box if ECU is unresponsive) checkbox.
4. Click Browse and select the same .bin.enc firmware file.
5. Click Program Firmware. The Updater runs an aggressive bootloader entry sequence to recover the sensor.

If Unbrick ECU still does not recover the sensor: try a different baud rate in the Updater (115200 / 230400 / 921600), close everything else on the COM port, and try a different USB port (preferably USB 2). Also verify the sensor is getting a clean, stable power supply — an unstable supply or a USB hub mid-flash can hang recovery. If you are still stuck, send QuSpin the full Updater console output from the failed flash attempt and a description of when the sensor became unresponsive — we can usually diagnose the remaining cases from the log.

To prevent future ECU lockups: follow the two prep callouts at the top of this page — match the baud rate and put the sensor in idle mode before clicking Program Firmware.

Still stuck?

Send QuSpin a copy of the full Updater console output (from Connected to COMN through the failure line) along with the sensor serial number and the firmware version you are trying to flash. We can usually diagnose the remaining cases from the console log.