I have discovered that the hex sequence {10 FF 10 00 xx} is the command to set the print darkness. Observed the app using values of 0, 2, or 4; intermediate values seem to work as well. Higher values don't seem to fail, but are not visibly different from 4.
You could add this as a feature, if you like... :)
EDIT:
It seems this command doesn't take effect until after the 12 null sequence is sent. (At least on the A9 I'm testing with. This script fully works with the A9 as far as I have tested. If you wanted to add more support for it, A9 print width is 0x48, 576 dots)
I have discovered that the hex sequence {10 FF 10 00 xx} is the command to set the print darkness. Observed the app using values of 0, 2, or 4; intermediate values seem to work as well. Higher values don't seem to fail, but are not visibly different from 4.
You could add this as a feature, if you like... :)
EDIT: It seems this command doesn't take effect until after the 12 null sequence is sent. (At least on the A9 I'm testing with. This script fully works with the A9 as far as I have tested. If you wanted to add more support for it, A9 print width is 0x48, 576 dots)