Teensy 3.5 | Paynter's Palace

Posted 20 December 2022

This post describes the actions I have taken to centralize the ‘board.txt’ and ‘TeensyOTA1.ttl’ (Tera Term macro) locations that facilitate the Teensy OTA capability, so that all my various firmware projects targeted at my wall-following robot all use the same set of files. This is done by using the Windows ‘mklink’ command to create ‘hard’ links from the various program folders to a single folder called ‘Robot Common Files’.

For the past five or six years I’ve been working on a 4-wheel robot project to autonomously navigate around my house using a (by now) fairly sophisticated wall-following algorithm. As I have worked through the various problems, I’ve gone through at least three different physical form factors, starting with a 3-wheel (two driven wheels, one castering wheel) and ending up (so far) with a custom 4-wheel ‘wide-track’ model.

Also along the way I have gone through any number of software versions. I work mainly with the Arduino ecosystem, but I don’t use Arduino directly. I use Microsoft Visual Studio 2022 Community Edition with the Visual Micro extension, and this is a great platform.

My latest hardware upgrade was to replace my original Arduino Mega 2560 processor with a Teensy 3.5 main processor, with a firmware update to achieve over-the-air (OTA) updates using a Wixel RF pair.

I now have at least twenty different software/firmware projects that I run on the robot for different reasons. I have a ‘main line’ project that incorporates all features required to full execute autonomous wall-following, and then I have lots of smaller projects aimed at exercising some small subset of the full feature set – things like distance calibration testing for the robot’s two 3-element VL53L0X time-of-flight distance sensors, and for testing out different ways of managing ‘rolling’ and ‘spin’ turns, and different algorithms for wall-tracking. All of these projects use the same ‘over-the-air’ (OTA) firmware/hardware configuration for firmware updates. Up until now I have been simply copying the two required files – ‘board.txt’ and ‘TeensyOTA1.ttl’ (a Tera Term macro) from project folder to project folder, but a recent Visual Micro update broke my OTA routine, and I discovered that having these two files copied into multiple project folders didn’t work so well – oops!

So, I decided to create ‘Robot Common Files’ folder in my Documents\Arduino folder tree, place these two files (along with the required FlashTxx.cpp/h files and my ‘enums.h’ file) into this folder, and then use the ‘mklink /H’ command (12/23/22 note: Admin privileges are not required) to create ‘hard’ links from each project’s folder to the single files in m Robot Common Files folder. The commands I used to accomplish this were:

//
//
C:\Users\Frank\Documents\Arduino\WallE3_AnomalyRecovery_V2>mklink /H board.txt "C:\Users\Frank\Documents\Arduino\Robot Common Files\board.txt"
Hardlink created for board.txt <<===>> C:\Users\Frank\Documents\Arduino\Robot Common Files\board.txt

C:\Users\Frank\Documents\Arduino\WallE3_AnomalyRecovery_V2>mklink /H TeensyOTA1.ttl "C:\Users\Frank\Documents\Arduino\Robot Common Files\TeensyOTA1.ttl"
Hardlink created for TeensyOTA1.ttl <<===>> C:\Users\Frank\Documents\Arduino\Robot Common Files\TeensyOTA1.ttl

C:\Users\Frank\Documents\Arduino\WallE3_AnomalyRecovery_V2>mklink /H board.txt "C:\Users\Frank\Documents\Arduino\Robot Common Files\board.txt"

Hardlink created for board.txt <<===>> C:\Users\Frank\Documents\Arduino\Robot Common Files\board.txt

C:\Users\Frank\Documents\Arduino\WallE3_AnomalyRecovery_V2>mklink /H TeensyOTA1.ttl "C:\Users\Frank\Documents\Arduino\Robot Common Files\TeensyOTA1.ttl"

Hardlink created for TeensyOTA1.ttl <<===>> C:\Users\Frank\Documents\Arduino\Robot Common Files\TeensyOTA1.ttl

where ‘WallE3_AnomalyRecovery_V2’ gets replaced each time with the actual project name

Now, when I want to edit either the ‘board.txt’ or ‘TeensyOTA1.ttl’ file, I can simply right-click on the filename in any project folder and select ‘edit with NotePad++’, and the single file in Robot Common Files gets opened for edit, and the changes are immediately available in all projects that use the Teensy OTA feature.

31 January 2023 Update:

After trying this trick a few times, I realized I had left out a step, so this update fixes that. Below is the entire Cmd line session for my latest ‘new project’:

Microsoft Windows [Version 10.0.19044.2486]
(c) Microsoft Corporation. All rights reserved.

C:\Users\Frank>cd C:\Users\Frank\Documents\Arduino\WallE3_Complete_V1

C:\Users\Frank\Documents\Arduino\WallE3_Complete_V1>mklink /H board.txt "C:\Users\Frank\Documents\Arduino\Robot Common Files\board.txt"
Hardlink created for board.txt <<===>> C:\Users\Frank\Documents\Arduino\Robot Common Files\board.txt

C:\Users\Frank\Documents\Arduino\WallE3_Complete_V1>mklink /H TeensyOTA1.ttl "C:\Users\Frank\Documents\Arduino\Robot Common Files\TeensyOTA1.ttl"
Hardlink created for TeensyOTA1.ttl <<===>> C:\Users\Frank\Documents\Arduino\Robot Common Files\TeensyOTA1.ttl

C:\Users\Frank\Documents\Arduino\WallE3_Complete_V1>

Microsoft Windows [Version 10.0.19044.2486]

C:\Users\Frank>cd C:\Users\Frank\Documents\Arduino\WallE3_Complete_V1

C:\Users\Frank\Documents\Arduino\WallE3_Complete_V1>mklink /H board.txt "C:\Users\Frank\Documents\Arduino\Robot Common Files\board.txt"

Hardlink created for board.txt <<===>> C:\Users\Frank\Documents\Arduino\Robot Common Files\board.txt

C:\Users\Frank\Documents\Arduino\WallE3_Complete_V1>mklink /H TeensyOTA1.ttl "C:\Users\Frank\Documents\Arduino\Robot Common Files\TeensyOTA1.ttl"

Hardlink created for TeensyOTA1.ttl <<===>> C:\Users\Frank\Documents\Arduino\Robot Common Files\TeensyOTA1.ttl

C:\Users\Frank\Documents\Arduino\WallE3_Complete_V1>

The first line above shows the ‘cd’ step, which I had left out of the previous post. After that, I just copy/pasted the ‘mklink….’ text for each of the two files, and then everything was wonderful again.

Stay Tuned,

Frank

A while back, I had some problems with damaged Teensy 3.5 main controllers on Wall-E3, my autonomous wall-following robot. I eventually traced the problem back to large voltage transients that occurred when I connected/disconnected the charging probe. These transients were conducted to the Teensy 3.5 pin used to detect the probe connection status, causing the Teensy to immediately reboot, and then eventually become unusable. I solved this problem by using a non-conductive photonic charger connect/disconnect system using the supplied charge LED on the TP5100 charger coupled to a photoresistor.

Unfortunately, I ran through most of my Teensy 3.5 stock while I was figuring this out, and now this part is unavailable from PJRC or anywhere else – maybe a victim of the world-wide chip shortage? The good news though is that the Teensys 4.1, successor to the Teensy 3.5 is available, so I purchased a few to evaluate as a replacement for the T3.5 on my robot.

The Teensy 4.1 has the same form factor and pin layout as the T3.5, which means it is a drop-in replacement in most cases. However, there are some gotchas. According to the comparison sheet on Paul Stoffregen’s PJRC site, the T4.1 is 5X faster (600MHz vs 120MHz) and has more memory. However, it doesn’t have any analog output DACs (T3.5 has 2), and more importantly, the T4.1 pins are not 5V tolerant!

To start my evaluation, I loaded a simple ‘blink’ program, and as expected it worked great. Here’s the test setup, utilizing my newly-discovered OONO breakout board.

After this first test, I am convinced that the T4.1 will work nicely as a T3.5 replacement, except possibly for the 5V tolerance issue. To investigate this, I looked at my current system schematic

Wall-E3’s main controller is directly connected to two VNH5019 motor controllers, several LEDs (the Chg Stat Display module), two INA169 current sense modules, a Pulsed Light (now owned by Garmin) LIDAR system via it’s ‘Mode’ pin, the ‘HC-05 BT Module’ (now replaced by my new 5V Reg/Wixel board) via its TX/RX pins, and the battery pack via the ‘Chg Conn’ pin (this the photonic connection discussed above). It is also connected to a MPU6050 IMU, a Teensy 3.2 running the IR charging beam detector, and another Teensy 3.5 running the 7-element VL53L0X distance sensing array, all via two different I2C ports.

The I2C ports are no problem, as they are either Teensy-to-Teensy or Teensy-to-MPU6050, which has an onboard regulator to regulate 5V down to 3.3, so the data lanes are 3.3V. The LED panels is passive (doesn’t generate any signals of its own), so that’s not a problem. The Wixel RF Transceiver inside my 5V Regulator/Wixel module runs on 3.3V, so the RX/TX lines are compatible with Teensy 4.1. The ‘Irun’, ‘Itot’ and ‘BattV’ A/D inputs are all below 3.3V at their maximum values (The Irun and Itot lines max out at about 2V (2 amps through the current sensor), while BattV maxes out at about 2.4V (8.4V max battery voltage minus 6V drop through a 6V zener diode).

The ‘Mode’ line on the LIDAR could be an issue. The original Pulsed Light LIDAR was acquired by Garmin, so the original datasheets are no longer available. The Garmin datasheet says that the MODE pin output is limited to 3.3V, but I don’t know if that is the same for the original Pulsed Light model I’m using on Wall-E3. So, I hooked up my digital O’scope to the LIDAR’s MODE pin on Wall-E3 and measured it directly. As shown in the following scope grab, the output is indeed limited to 3.3V – yay!

Pulsed Light LIDAR-Lite MODE pin pulse output. Note max amplitude (Ma) = 3.308V

So, it looks like I can drop a Teensy 4.1 into Wall-E3’s system and it should do fine. I don’t really need the speed and/or memory improvements, but I do need a replacement for the now-defunct Teensy 3.5, in case I manage to kill yet another one.

21 March 2022 Update:

I took the time today to see how (or if) the Teensy 4.1 breakout module would fit on my current Wall-E3 robot. As shown below, it’s pretty big!

Based on the above photos, I don’t think this breakout board has a future on Wall-E3. Even though the module will fit, that doesn’t take into account the fact that the wiring from the module will extend horizontally from the module, rather than vertically as it does with the plain ‘Teensy + Female header’ arrangement. It was a great idea a the time, but I guess the reality is that the breakout module will be relegated to testing,

Stay tuned,

Frank

Paynter's Palace

Tag Archives: Teensy 3.5

Using mklink to centralize Teensy OTA Files

31 January 2023 Update:

Teensy 4.1 Replacement for Teensy 3.5?

21 March 2022 Update: