Matrix Orbital LK204-24-USB - Manual (Page 13)

2.1.5 Serial TTL Communication
Figure 7: Rx / Tx LED Header
The display can also be talked to at TTL (logic 0V to +5V) levels. This will allow TTL communications
through the 4-pin header. Communicating by Serial TTL will bypass the USB components and power will
be required to be provided by this header.
8bit, no parity, one stop bit.
Speed: 19.2 Kb/s.
NOTE Do not power or communicate by USB and Serial TTL at the same time.
2.1.6 LED Headers
The LED headers provide a visual indication of communication over the Rx and Tx line if a LED is
connected. The LEDs blink frequency will increase as the amount of data increases. The headers are current
limited to 20mA at +5V. This feature only works with USB communication and will not work with Serial
TTL.
2.2 General Purpose Outputs
The display has a number of general purpose outputs for a variety of applications.
Matrix Orbital LK204-24-USB 9