ePot.V3 firmware updating

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This document applies to the ePot.V3 firmware used in the V3 Max and Mini series of electronic stepped attenuator & preamp controller and V3 model preamps.

What is firmware?

All of Tortuga Audio’s preamp’s  are controlled by a microcontroller which is a type of embedded microprocessor widely used in commercial, industrial and consumer equipment. The software running on the microcontroller is referred to as “firmware”.

Firmware is a class of computer software that controls a specific hardware device and is typically stored in that devices’s read only memory. By its nature firmware is neither easy to erase nor is it easy to replace or update especially as compared to software applications that run on a personal computer. Firmware usually runs directly on a microcontroller’s “bare metal” without any intervening operating system.

Why update your firmware?

The simple reality is that all software have bugs. Most of the time the casual owner of equipment can ignore them. But sometimes the bug is significant and needs to be fixed. And sometimes we simply make improvements and add features you might like to have. In either cause, the only way to get the fix or improvement into your machine is to do a firmware update.

Firmware versions & changelog

Firmware for the ePot.V3 is common to both the Mini and the Max. That means there’s a unified common source code used for both the Mini and the Max. The firmware versions shown in the changelog below  reflect this commonality and applies to both the Mini and Max.

However, the Mini uses a 64 pin microcontroller while the Max uses a 100 pin microcontroller and thus the pin assignments are different. Moreover, certain functionality present in the Max is not present in the Mini. As a result, the firmware download files for the Mini and Max are NOT identical and are NOT interchangeable. You must download the Mini firmware file for the Mini and the Max firmware file for the Max. 

The firmware changelog listed below reflects mostly minor bug fixes, “under the hood” changes/improvements over time and sometimes a feature addition. Unless you’re having a specific problem with your current firmware, updating to the latest version is not generally warranted. However, significant revision it will be marked ** Important **.

3.3.0 - 9.1.22* Change - Major rework of code (refactoring) used for software timers and numerous related items. This was a maintainability update.
* Fix - Cal Auto was not displaying the elapsed time properly - may still have some issues.

Note: This revision, along with prior revision 3.2.8., both involved significant reworking of the software "under the hood" without changing any of the features or functionality. These changes were tested but not exhaustively. Balanced application has NOT yet been tested. None of the recent revisions have any direct bearing on sound quality.
3.2.8 - 8.16.22* Change - Major rework (refactoring) of code related to the configuration of all input/output pins. This was a maintainability update.

3.2.7 - 8.1.22* Fix - Switching status flag was not getting reset after input switching completed due to a bug introduced via 3.2.6
3.2.6 - 6.28.22* Fix - Numerous bug fixes and changes related to operating dual V3 boards in balanced audio mode
3.2.5 - 5.27.22* Fix - Precal access password was not allowing escape back to parent menu or exit to volume control. Note that this is not an accessible user feature.
3.2.4 - 5.19.22* Fix - Control was not reverting to volume control after completion of Reset
3.2.3 - 4.14.22* Fix - Some control menu items for Mini were missing their return to default volume control
STM32 Cube Programmer
Version 2.10.0 - 4.4.22
Updated STM32 Cube Programmer application. As of this updated version, there are now separate application versions for windows 32, windows 64, and Apple MAC. We highly recommend you update to this latest application prior to updating your V3 preamp's firmware.
3.2.2 - 4.8.22* Fix - Bug was found that only applies to the ePot.V3 Max. Caused calibration data to appear to be lost for default impedance setting #1 each time preamp was turned off, but only if Cal setting was set to some other setting than #1 at the time of power down. This required Cal to be run again each time preamp was turned back on. The default #1 Cal data wasn't actually lost but preamp thought it was. This bug was introduced in revision 3.2.0. This only applies to you if you currently have firmware 3.2.1 or 3.2.0 in a Tortuga Audio Max controller board or finished Tortuga Audio preamp.
3.2.1 - 3.9.22* Change - Control menu item "Vol Muting" replaced with "Buf Control" to include both enabling/disabling of buffer muting and also switching the J7.X2 and J7.X3 pins between buffer/trigger and trigger/buffer.
3.2.0 - 2.24.22* Change - Refactored all controls at base class level and all derived classes eliminating use of command() function and instead using OOP methods for each command
3.1.1 - 1.14.22* Fix - The volume steps/units option was not being saved - setting lost when unit powered down
* Fix - Added missing initialization check on volume steps/units
3.1.0 - 1.08.22* Tweak - Partially removed unused code for STM32F107/V25 application.
3.0.7 - 12.09.21* New - Updated to accommodate OEM option Pandora Audio Lab including Pandora logo
* New - Added About menu item for showing Tortuga Audio "inside" - active only for Pandora Audio
* Fix - Turning off preamp via Encoder was not working
3.0.6 - 11.16.21* Tweak - Refactored resistance measurement function used during calibration
* Fix - Ensure Mono disabled in V3 revisions other than Rev A
3.0.5 - 11.11.21* Fix - Control menu on Mini was skipping Version info display
3.0.4 - 10.21.21* Fix - Volume level of 0 was not being bumped up to min value of 1 when being unmuted.
3.0.3 - 10.19.21* Fix - MaxVol on change was not working correctly with FreeRTOS

3.0.2 - 10.12.21* Fix - Auto On was not working properly with FreeRTOS
3.0.1 - 10.11.21
** Important **
** Major Change **
* New - Application converted to using FreeRTOS - "real time operating system" - initial release
* Change - all timers converted to FreeRTOS
* Change - all SPI now use Mutex around chip selects to avoid collisions
* Fix - Display timeout timer setting wasn't being saved
* Fix - ScreenSaver wakeup was not immediately suspending screensaver task
resulting in delayed response to encoder inputs
2.3.1 - 9.13.21* Tweak - Moved start-up delay during Cal so display would respond faster
* Fix - Encoder input via push/turn was not being sent to slave board
* Tweak - removed redundant #define for _Init_Key
* Fix - Auto power-on was double-firing in slave board
* Fix - Added auto power-on default disabled code
2.3.0 - 8.25.21* New - In addition to the existing procedure for turning off the preamp by
going to the "Off" menu item, you can now escape out to the "Volume" menu
item by pressing Menu and then turn off the preamp by immediately pressing
the Mute (lower right) button.
* New - There's a new menu item "On" above the "Off" menu item. "On" allows the
user to enable/disable automatic power on such that the preamp is left in
a turned on state rather than the default turned off state when power
is applied to the preamp.
2.2.7-9 8.18.21* New - Set all unused pins to output/lo except the 2 SWD pins
* Tweak - Changed object names of all used gpio pins to start with "gpio_"
2.2.6 - 7.29.21* Change - Default impedance set to 75k for _LDR3000X_TUBE models
* New - Added output for Cal relay used by new Tube & SolidState buffer boards during Cal to isolate
buffer boards during Cal
* Tweak - cleaned up encoder coding
* Tweak - cleaned up OLED DMA/SPI coding
2.2.5 - 7.20.21* Fix - Made sure volume gets updated immediately after Cal stopped so it didn't start a full volume after Cal
2.2.4 - 7.15.21* Change - Reset now resets everything except precal data (only cal data before)
* Change - Removed offsets menu item - no longer needed
* Fix - Channel balance with balanced audio was not working properly
* Change - Master is now told by attached slave that it is balanced audio mode each time slave
receives a power_on command from the Master. Results are no longer saved/read at power up.
2.2.3 - 6.11.21* Fix - Corrected impedance read on attenuation module eeprom on Mini
* New - First release for V3 Max in balanced configuration.
2.2.2 - 5.7.21* Fix - New volume ramping option was not being initialized - defaulted to no ramping
2.2.1 - 5.5.21 * Change - Disabled volume ramping while cal active to avoid volume setting conflicts during cal
2.2.0 - 5.4.21
** Important **
** Rev 2.2.0 marks first release of Rev B Max board **
* Fix - Removed stray pixel from upper left corner of display. Was due to not clearing buffer after single byte DMA.
* New - Added various code unique to V3_Rev B board
* Change - Mini only - made LED flash 4 times when channel balance reset to neutral
* New - Added Vol Muting menu item to allow enable/disable of muting relay.
* New - Added Vol Ramp menu item to give user volume ramping options.
* Change - Updated precal.cpp & cal.cpp to improve stability during precal/cal processes
* Change - Switched to flash latency 4 from latency 3 just to be safe in clock_main.cpp
* Change - Reorganized precal factor routines
* Change - Modified input switching timing, sequencing and ramping to conform with new Vol Ramp methods
2.1.3 - 3.23.21* Fix - Intermittent bug introduced with 2.1.0 that sometimes stopped the Apple remote repeat command
2.1.4 - 3.30.21* Tweaks - Minor tweaks to adapt existing code to possible future FreeRTOS option
2.1.2 - 3.18.21* Change - Moved all inputs/outputs to new Class
* New - Added some prelim code for _V3_RevB board
* New - Added MuteRelay output for _V3_RevB board
2.1.1 - 3.12.21* New - added hardware types V3_RevA1 (new power board) & V3_RevB (updated rev B Max board)
* Change - numerous edits to get F107 version to compile
* Change - minor revision to code for muting
2.1.0 - 2.19.21* New - Commissioned the Master/Slave communications for balanced audio control for the V3 Max.
* New - Added Board menu item to allow designating each board as Primary (master) or Secondary (slave). When boards are connected, setting the Master to Primary forces all connected boards to be slaves.
2.0.3 - 2.2.21* Fix - Current volume was not being saved when changing inputs with VolControl set to "Input"
2.0.1 - 11.17.20* Fix - SPI DMA was blocking power turnoff on the Mini during turtle fade out
2.0.0 11.12.20
** Important **
* Fix - Version 2 marks the fix of a chronic bug that would cause the V3 Mini and Max to lock-up intermittently. This problem did not manifest in all units. The problem was due to an overly aggressive microcontroller clock setting.
1.1.1 - 10.29.20* Fix - LED not blinking during mute
* Fix - All SPI send code updated to ensure DMA turned off prior to sending data to SPI without DMA
* Change - Related to fix above, moved all SPI chip selects into special function to ensure uniform action with respect to SPI/DMA and to avoid colliding SPI calls.
* Change - Updated compiler from C++14 to C++17
* Change - Moved encoder inputs back under interrupt control
1.1.0 - 10.20.20* Change - Converted OLED display code over to c++ classes
* Tweak - Turning off via encoder now shows "Off" briefly before shutting down same as with remote
* Change - Converted OLED RAM SPI write to DMA driven which allowed reducing SPI clock speed from /4 to /32 same as the V25 reducing SPI noise
* Change - Made screensaver Tortuga movement periodic rather than continuous feed in order to minimize audible artifacts from SPI data bursts.
* Change - Improved responsiveness of controls and screen updates by moving from polling to interrupt driven
* New - Grouped all SPI chip selects into single subroutine to ensure only one CS low at any time.
1.0.9 -10.07.20* Change - Moved LED blinking timer from polling to interrupt driven
* Fix/Change - Auto detect of status LED in Mini was not working as previously tested. Changed this to adding a jumper across OLED.DC pin and ground and testing this an input during bootup.
* Fix - Corrected missing port/pin initialization
* Change - Revised encoder logic to improve performance
* Change - Channel balance offset in Mini is now applied equally to one side positively and to the other side negatively such that total volume remains roughly the same. Before the offset was applied entirely to one
side or the other.
* New - PanelLED will now flash quickly 5 times when channel balance bias hits zero mark.
1.0.8 - 9.28.20* Change - Updated eeprom class to allow direct access to working "value" .
* Change - Numerous changes to simplify interrupt handling and improve stability
1.0.7 - 9.24.20* Tweak - Added automatic model name width calc to center model name in display
1.0.6 - 9.18.20* New - Commissioned control interface between Max and SSPB.V1 solid state buffer board for new LDR300x preamp
* New - Added model name to display startup splash
1.0.5 - 9.16.20* Fix - Current input was not being shut off during mute even though volume was minimized - some sound would still bleed through
1.0.4 - 9.8.20** Initial release for Max **
* Changes (Max) - numerous revisions/changes under the hood that are relevant only to the Max
* Change - Revised internal system for storing setting data to eeprom
* Change - Removed encoder type menu item for both Max and Mini - wasn't relevant to the V3
* Change - Converted encoder decoding to simplified state machine logic - polling only - no interrupts

1.0.3 - 8.28.20* Change - Updated to software timer code to improve clarity and reliability
* New (Max) - Added automatic Cal start. User can adjust from 0 days (off) up to 365 days (1 year). Default is 30 days. Cal will only start automatically when unit is turned off.
1.0.2 - 8.26.20 * Change - Major revision of UART serial communications section in preparation for handling balanced systems (all under the hood stuff relevant only to the Max)
1.0.1 - 8.20.20* New - Added default input impedance to info display
* Fix - Display timeout period was not being stored properly
1.0.0 - 8.18.20* New - Initial release for ePot.V3 Mini

Which firmware version do you have?

You must have an OLED display attached to your V3 in order to tell which firmware version you currently have. The firmware version is shown by selecting the “Version” menu. The firmware version is displayed as a 3 digit number as for example “FW: 108”

Firmware updating overview

Before wading into the detailed firmware updating procedure described below it’s helpful to have an understanding of the overall process and tools required.

The firmware updating process can be summarized as follows:

  1. Start with your V3 board/preamp powered down (not just turned off but unplugged from power)
  2. Download the updated firmware file from our website to your computer
  3. Connect your computer to the V3 with USB cable. If you have a DIY board/preamp make sure the USB-to-Serial adapter/cable is properly connected to the V3.J3 header
  4. Start the firmware programmer application on your computer, select the USB connection, and select the firmware file you had already downloaded
  5. Apply power to your V3 board/preamp and then turn it on
  6. Place your ePot.V3 into bootloader mode but following the menu tree down to “Firmware”, select it, and then press Enter button on your remote 5 times to place the preamp into bootloader mode
  7. Establish live connection between the programmer application and your V3
  8. Initiate the firmware download into your V3 by your programmer application
  9. Disconnect the USB cable and shut down your programmer application.

The USB cable

A USB cable is required to connect your computer, that is running the programmer application, with the V3, that is running the bootloader application.

If you have one of our finished V3 preamps, then you only need a plain USB cable with a Mini B plug on one end and the common type A plug on the other.  The Mini B plugs into your preamp and the type A end plugs into any of your computers USB ports.

If you have one of our DIY V3 Mini or Max boards things are a bit more complicated because the V3 does not accommodate a direct USB connection. Instead, the V3 has a serial data (UART) port that has RX (receiver) and TX (transmitter) pin connections. Fortunately, there are many specialized USB-to-Serial cables and also USB-to-Serial adapters available for typically $5-10 that take care of this USB-Serial conversion.

The links below will take you to a couple of examples of these type specialized cables or adapters to be used with plain cables.

The bootloader

In order to update the V3 firmware you need to place the V3 into “bootloader” mode. The bootloader is a specialized application that resides on the V3’s microcontroller whose sole purpose is to facilitate firmware updating. We did not create the bootloader application. It was loaded into the V3 microcontroller by the microcontroller manufacturer at the chip factory. You never have to worry about damaging or erasing the bootloader application. It resides in protected memory on the V3 controller chip.

You must start the bootloader application in order update the V3 firmware. There are 2 ways to start the bootloader program.

The first and easier way is to go to the V3 OLED display and scroll down the menu list to the “Firmware” menu item and select it. Follow the instructions on the display to start the bootloader. The display screen may go blank or you may see a message and the V3 will appear non-responsive. This is normal. It is now in bootloader mode waiting for a query from the programmer application running on your computer.

The second and more awkward way is to go to your Mini or Max board and find the S1 (Reset) and S2(Boot) pushbutton switches on the board. First press/hold down the Boot push button and then while still holding down the Boot switch also press/release the Reset button and only then release the Boot button. Nothing obvious will happen when the V3 enters bootloader mode. That’s normal and that’s OK. Read on.

STM32 Cube Programmer application

The STM32 Cube Programmer, a.k.a. the “programmer”, is a powerful multipurpose microcontroller programming application that will run under Microsoft Windows and the Apple MAC OS. The programmer is maintained and made available for free by the manufacturer of the microcontroller used in the ePot.V3.  You have to download this application and install it on your computer before proceeding with any firmware update. You only have to do this download/install once.

We use the programmer to communicate with the bootloader through a USB connection. During the firmware update process the programmer erases the existing firmware and then uploads a new version.

You can download the programmer via the link below. The download is a zip file that you’ll have to unzip. Once unzipped you’ll be able to install the programmer by clicking on the installer program.

Starting with the release of version 2.10.0 in March, 2022, the STM32 Cube Programmer comes in different versions depending on whether you have a 32 or 64 bit version of Windows or if you use a MAC.

You only need to download and install the programmer application one time and not each time you update firmware.

The firmware file

The final piece of the puzzle is the updated firmware file itself that you are going to download into the V3. You retrieve this file directly from our website by clicking on the download link below. Store this data file somewhere on you computer since you will need to find it later using the programmer application.

There are 2 distinct download files listed below. If you have a finished Tortuga Audio preamp that ends with a “.V3” designator, or a DIY ePot.V3 Max controller board, only download the “Max” version and not the “Mini”.  If you have a DIY ePot.V3 Mini, only download and use the “Mini” file version.

Detailed instructions

Step 1 | install the programmer application

Download the programmer files from the download link above. Install the programmer application on your Windows, MAC or Linux machine. You may also have to download the Oracle Java application which is required to run the programmer.

We do not currently provide detailed instructions on how to install this application. It installs like most any other personal computer application.

Step 2 | start the V3 bootloader

Via OLED menu
Owners of V3 preamps with an OLED display can scroll down the menu list and select “Firmware”. Then press the Enter (center) button on the remote 5 times in a row. On the 5th press, the V3 will enter into bootloader mode. The OLED display may show a message confirming it’s in bootloader mode or it might also be blank.

At this point the V3 will have become non-responsive to any further control inputs. This is normal. Carry on.

No OLED display
Owners of V3 based preamps that have no OLED display need to place their V3 Max or Mini boards into bootloader mode using the S1/S2 (Max) or  S2/S3 (Mini) pushbuttons located on the board. Follow the pushbutton sequence below.

  1. Push/hold-down the Boot pushbutton
  2. Then push/release the Reset pushbutton
  3. Finally, release the Boot pushbutton

At this point the V3 will have become non-responsive to any further control inputs. This is normal. Carry on.

Step 3 | start programmer application & select UART

When you start the programmer application it will probably look like the image below.

The first thing to do is click on the blue pulldown menu labeled ST-LINK, and select the UART option instead.

Step 4 | configure the UART port & connect the cable

Follow these substeps:

  1. Don’t connect the USB cable yet! If you’ve already connected it, disconnect it from the V3 preamp.
  2. Pull down the Port menu list and note the current available port names. None of these are the correct port because the USB cable is currently disconnected.  Abandon the Port pulldown men for now.
  3. Next, plug the USB cable into your computer and also into your V3 preamp Mini B port.
  4. Pull down the Port menu list again and this time note the new port name. This new port name is the connection to the V3. Select that port.

Step 5 | select the firmware file

To get the programmer to look like the image below you first have to click on the downward facing arrow icon on the left side bar to change the view to “Erasing & Programming”.

Then click on the “Browse” button and select the firmware file that you had downloaded and stored earlier.

Please also check the box labeled “Run after programming”

Step 6 | establish communication between programmer & bootloader

To summarize where we are at this point, you have already started the bootloader on your V3 preamp, the programmer applications is running, you’ve connected the USB cable between your computer and preamp, and you’ve selected the correct UART Port.

The next step is to establish communications between the programmer application (on your computer) and the bootloader application (on your V3 preamp). To do this press the green “Connect” button in the upper right hand corner of the programmer application.

This step is where you are most likely to encounter a problem where the programmer is not able to establish a connection with the bootloader. There can be several reasons for this but the most likely reason is that the V3 preamp bootloader has not been started or has quit. Go back and repeat Step 2 and then jump back here to step 7 and try again.  You may also want to double check step 6.

Step 7 | transfer the firmware

If you’ve made it this far you almost done. You are connected as evidenced by the green circle and “Connected” message in the upper right hand and  also the running “log” info in the log window.

The last step is to start the transfer of the firmware file into the V3 preamp but clicking on the “Start Programming” button. The horizontal green progress bar at the bottom of the screen will show the firmware file transfer progress. The transfer should take less than a minute to complete.

When the transfer is complete the V3 preamp will reboot and in doing so will disconnect from the programmer application. As a result the programmer will likely report some errors that it has lost communication with the V3 preamp. That’s normal.

At this point your V3’s firmware has been updated. You can proceed to disconnect the USB cable, shut down the programmer application, and operate the V3 preamp as usual.

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