Sunday, 27 December 2020

Strange serial port issue with Arduino nano 33 sense ble

Serial port problems with Arduino nano 33 sense

Can't upload sketch / Can't connect via Putty or serial monitor

I gave myself a nano Christmas present: A brand new Arduino Nano 33 Sense BLE. Mainly because I wanted to try out machine learning with TinyML, but the book from O'Reilly is still in the mail.

Tiny, but with lots of sensors

So I started exploring Bluetooth LE, trying to master that skill first. It was a slightly bumpy ride because from time to time the Arduino IDE switched the serial port to COM5, while the Arduino clearly was on COM7 (these will very likely be different on your PC)

The nano 33 on COM7

I reset the arduino a couple of times, but I couldn't get it to communicate via COM7, although the port was clearly present in Windows.

Double click the reset button

More or less by chance I double-clicked the reset button. And - whatdoyouknow - I had the Nano on COM5. - How strange!

The nano 33 on COM5
Now I could upload sketches again. - Ok. But COM port assignments in Windows don't change without a good reason. Let's dig deeper.

USB device tree viewer

Uwe Sieber has published a great, free tool "USB tree viewer", that shows all the details of all attached USB devices. I can then copy both (the COM7 and COM5) configurations to Notepad++ and run the Compare-Plugin.

As expected, the double click on the reset button lets the nano 33 appear as a very different device:

While the Vendor ID is alwaysd 0x2341 (Arduino SA), the product ID changes from 0x805A to 0x005A. The device ID, revision number and sleep modes also change.

The device descriptor string 2 changes from "Nano 33 BLE" to "Arduino Nano 33 BLE" string descriptor 3 is the same, but padded with leading "0"s.

Looks like two different devices

No wonder Windows sees that as a new device. I have no idea what the point in all that is.

Please leave a comment if you have more info.


EDIT 20210107:
The behavior is actually documented in the documentation:

If the board does not enter the upload mode, please do a double press on the reset button before the upload process is initiated; the orange LED should slowly fade in and out to show that the board is waiting for the upload.

I still find the "nano 33 ble sense" rather unpleasant to work with because of that.

Friday, 25 December 2020

Macbook late 2008 SSD upgrade

Macbook SSD upgrade

With only 2GByte of RAM and an out-of-support El Capitan (OSX 10.11), the 12 year old MacBook is somewhere between "ready for recycling" and "too good to waste". Over time it had become unbearably sluggish. So with prior good results on Windows PCs from the same era, I decided to give it a go.

It is super easy and reasonably safe even for intrepud beginners.

SSD selection

I tend to go for maior brands whenever affordable. Amazon had a 500GByte Samsung 860 EVO for cheap on Black Friday 2020, so that ist the SSD of choice. The person using the Mac as a mail and browse machine will never even come near the full capacity of that disk.

Preparations / backup

A full time machine backup on an external USB drive is all it takes to recover the installation to a new SSD.

Physical installation

These old devices are built to last and to be serviced: Just remove the bottom cover (unlock with lever). Remove the disk holder (black plastic bar) with a small Phillips screw driver and lift out the old disk by the pull-tab.

Carefully remove the SATA connector from the left side of the old hard disk.

Remove the four small bolts that held the disk in place and install them on the new SSD

Reconnect the SATA connector

Insert the SSD and fix it with the plastic bar.

Close the battery/harddisk cover.

SSD preparation

Attach the USB drive with the Time Machine backup to a USB port.

After a little wait, the MacBook will boot from the USB drive.

A menue comes up: There choose the hard disk utility and add a partition to the SSD (accept the first file system option).

Go back to the previous menu

Restore from Time Machine Backup

Choose your Time Machine Backup Disk and select the latest backup.

Wait for the restore to complete

Wait for the restore to finish and reboot

Tell the Mac where to boot from

It speeds up the boot process a lot when you set the new SSD as the boot device in the settings. Otherwise it takes a while to find bootable devices.

That relatively cheap upgrade saved the nearly unuseable machine from the junk yard. With only two 1GByte RAM modules installed, the next option is to go for more memory. With the last published firmware version, this machine supports up to 8GByte.


Friday, 4 December 2020

Inside an AMG8833 thermal imager

Very simple AMG8833 thermal imager


(I took it through it's paces in this video)

For years I had felt he need for a thermal imager or thermal camera to help me find faulty electronic components. But the price tag was prohibitive.

40mA - not very power hungry

I experimented with a single temperature sensor, sweeping a range with model servos. Interesting and entertaining, but not really useful. That was back in 2013. Even later, the cost for the simplest "grid eye" was still a bit on the high side for an experimenter. Until recently.

Bare bones imager

I then found this bare bones / no frills thermal camera here on Banggood. It comes without any matching documentation, let alone a manufacturer name.

PCB Version 5.1.2 from June2020

It has a resolution of 8x8 pixels and sports the "high gain" version of the Grideye. While "high gain" sounds like a good thing, it actually limits the sensor's thermal range to 0-80 degree centigrade.

The AMG8833

The Panasonic GridEye comes in different flavours that is easy to decipher from the part number:

The 88 stands for the 8x8 pixel resolution, the next digit shows the operating voltage 5 for 5volts, 3 for 3.3 volts. And finally a 3 for the "high gain" and a 4 for the "low gain" version, with the low gain version ranging from -20C to 100C. We don't have that in this device so on very cold days, the outside world looks like a blank sheet to the imager.

The next step up is the 32x24 pixels MLX90640 from Melexis, which has a -40 to 300C temperature range. Looking at what 8x8 pixels can do, 32x24 should be awesome. It comes at about twice the cost of the AMG8833 based imager, also from Banggood.


Electronics repair

It all boils down to the question: are 8x8 pixels sufficient to identify hotspots in a faulty device?

44c after just a few seconds
With it's 60degree field of view, working close-up gives enough contrast to identify individual hotspots. One thing to notice is that the colour scheme is autoscaling. So "red" just means warmer than the surrounding area, not necessarity hot. The colors are spread over the range currently detected by the sensor. The good aspect is that it always gives the best contrast possible, the downside is, that it can be very irritating.

The microcontroller

The GD32 ARM Cortex-M3 Microcontroller

Quite a capable little 32-bit RISC microcontroller from GigaDevice's "Value Line". See the data sheet here for details. The GD32F130F4P6 is the simplest of the DG32F130Fx family in the TSSOP20 package, sporting 16kByte of flash memory.
This thing appears to be pretty much a clone of the STM32F103x4 and might well be programmable with a ST-Link programmer. (haven't tested that).
The earlier 1.1 version, for which Banggood has a schematic diagram available, had a STM32F103C8, which essentially has the same performance, but more (64KBytes) of flash memory. So they obviously cut costs here a little on their way to Version 5.1.2

Final words

At a price point around 50 EUR/USD, this is not only a great experimenter's gadget, but very useful to track down thermal problems. Certainly no match for a full blown thermal camera, possibly even with a visual overlay - the cheapest models starting at three times the cost of this device.
The 0-80C temperature range can also be a maior limitation, depending on the intended use.
For me it is way better than sniffing out hotspots on PCBs or burning my fingers on them.