Q: Why is my Zymkey "invisible" to the i2c-tools suite?
A: Some people have become accustomed to using i2c-detect to do a first level check for correct installation and baseline functionality of i2c devices. However, these tools only really work if the i2c device communicates via a protocol that sits on top of i2c called SMBus or SMB (System Management Bus). Instead, Zymkey communicates to the host at a much more fundamental level, in part because the Zymkey protocol traffic is encrypted. While we're on the topic, perhaps i2c-tools should have been called "smb-tools"?
Q: Why does the LED continue to blink rapidly? It never blinks with the described pattern of once or three times every three seconds.
A: Check the following:
Make sure that you have enabled i2c support using raspi-config BEFORE your install the software. Also when you enable i2c communications be sure to follow the enable-disable-enable sequence.
If i2c support has been enabled correctly and the Zymkey LED is still rapidly blinking, check proper physical installation of the Zymkey as detailed in this "Getting Started" guide.
Check that the Raspberry Pi power is sufficient. The red LED on most Raspberry Pi models indicates if the Pi is being powered adequately. If it is not lit at all or flashes intermittently, try a different power supply or a different USB cable.
Zymkey uses GPIO header pins 3 and 5 for i2c communications and pin 7 as an interrupt signal to the Pi. Pin 7 should preferably be dedicated exclusively to Zymkey. Other devices may share the i2c bus with Zymkey, but there may still be address conflicts. By default, Zymkey uses slave address 0x30. If the address conflict cannot be resolved on the other i2c devices, there is a way of changing the i2c address on the Zymkey via the command line on the Pi (coming soon!). Using this application, the Zymkey address can be changed anywhere in the ranges of 0x30-0x37 or 0x60-0x67.
if the directory at /var/lib/zymbit or any of the files and/or subdirectories are corrupted or deleted, the Zymkey will fail to work.
IMPORTANT: if this happens when the Zymkey is locked (i.e. Production Mode), the Zymkey can never be used again.
Q: The LED blinks rapidly when booting, but eventually turns off. It doesn't blink once or three times every 3 seconds as described.
A: This issue could be caused by the same issues described in the first question (Why does the LED continue to blink rapidly?). Additionally, this can be caused if a locked (Production Mode) Zymkey is moved to another Pi.