Hi how can I send 8-byte or longer char strings?? ie:
SYSTEM
TEST 1 OK
This message is sent from the system to the DIGITAL FUEL DISPLAY the display is composed of 2 x 8 smart LED display hdps-2111 which can be addressed separately. I can address all eight displays separately. So maybe:
display 0/1/2 where 0 is a command?
char 0 - 7
alpha letter
ie to write to the entire display would take 16 writes 
plus I have to be able to send commands to it like reset and clear
or
can I create a “custom” for this device which will take 8 chars at a time.
You can define your own type:
uint8[<=2*8] text
And assign a dedicated subject per display. Alternatively, you can throw a key field in there and share the same subject for all displays, depending on your objectives:
uint16 display_id
uint8[<=2*8] text
Or you could just use the standard type uavcan.primitive.String.
Thank you!!