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I am debugging some code that requires a peripheral plugged into the phone’s USB port so I needed to be able to run adb’s logcat (and install functions) over WiFi. I found this page with the information required, the key points are repeated here for convenience.

The phone needs USB and WiFi debugging enabled in Settings->System->Developer options.

Plug the phone into the PC and enter the following on a console terminal:

adb tcpip 5555
adb connect <ip address of phone>

The phone can now be unplugged from the PC and the peripheral connected instead. As usual, to install an apk, use:

adb install -g <filename>.apk
adb logcat

I need a fast PC for some current work and decided that it’d be nice to use an NVMe SSD to speed up storage. I am using an Intel 750 PCIe 3.0 x4 add in card as it’s a simple way to go. Ubuntu has the NVMe driver built in so it came up straight away as /dev/nme0n1. One small issue is that gparted doesn’t seem to think this is a disk so it’s a case of reverting to old school command line stuff to get it set up for use.

First off is to create a partition:

sudo fdisk /dev/nvme0n1

Choose “n” to create a new partition, then “p” then “1” to create a new primary partition. Just use defaults for the sector numbers. Then “w” to write the data to the disk.

To create a file system on it:

sudo mkfs -t ext4 /dev/nvme0n1p1

Then create a mount point somewhere convenient:

sudo mkdir /media/nvme

Then mount the new partition on that mount point:

sudo mount /dev/nvme0n1p1 /media/nvme

At this point, the whole thing belongs to root which may not be what’s wanted. To change the ownership to a specific user (with the partition mounted):

sudo chown -R <user>:<user> /media/nvme

To get it to mount every time, add a line to /etc/fstab:

UUID=<nvme UUID> /media/nvme ext4 defaults 0 0

To find the UUID, enter:

sudo blkid

and then cut and paste the UUID for the NVMe drive.

To get some idea of performance, the hdparm command can be used.

Try:

sudo rm -rf /Library/Developer/CommandLineTools
xcode-select --install
sudo xcode-select -s /Library/Developer/CommandLineTools

I have to say that I consider the whole process of developing with Xcode deeply annoying. I recently had a problem where it claimed that I needed to set a development team for signing even though I already had. After spending a lot of time deleting, recreating projects etc etc, I realized that clearly Xcode was keeping some information elsewhere that was causing the problem.

Turns out that it caches some information in:

~/Library/Developer/Xcode/DerivedData

Each project has a folder here. I deleted any folders that had the same name as my project and that fixed the problem. Ugh. And don’t get me started on bitcode…

Many physical variables are best represented as floats and sometimes it is necessary to pass these variables across a network link. Floats are very standardized and can be safely passed around between different architectures and operating systems but need to be converted to a byte stream first (something like JSON can send floats as strings but this is pretty inefficient in time and space). In C or C++ this is pretty easy but Java is strongly typed and doesn’t make it easy to convert a float value to a byte stream and vice versa. However it can be done…

public void convertFloatToByteArray(float f, byte[] b, int offset) {
   ByteBuffer.wrap(b, offset, 4).order(ByteOrder.LITTLE_ENDIAN).putFloat(f);
}

public float convertByteArrayToFloat(byte[] b, int offset) {
   return ByteBuffer.wrap(b, offset, 4).order(ByteOrder.LITTLE_ENDIAN).getFloat();
}