I am trying to decide between using a Micro Maestro and a custom micro solution for controlling 4 servos at up to 50Hz ie position command updates.
The intention is to connect the Micro Maestro to my main controller board and communicate using the TTL serial interface using the compact command protocol.
My question is what is the minimum delay between subsequent commands to the Maestro ?
You should not need to use any delay between sending serial commands; you can send TTL serial commands back-to-back. When doing so, the time between commands would be determined by your baud rate.
I had assumed since the protocol is sending binary data (yes ?) there may be a requirement for some delay for the Maestro to sync with the first byte of the next command eg if somehow a position (period) word contains the 0x84 value, there is a chance for some confusion.
Another question I have is will the Maestro accept a 3.3V level serial signal ?
Yes, the protocol is sending binary data. A new command is specified by a byte with its most significant bit (MSB) set as mentioned in the “Command Protocols” section of the Maestro controller’s user’s guide. One exception of this is the Mini SSC protocol. If the Maestro received a 0xFF byte, it designates the start of a Mini SSC command, so the next two bytes will be interpreted in a special way.
As far as using 3.3V TTL serial signals, the Maestro might be able to receive 3.3V TTL serial bytes, but it is not guaranteed to read 3.3V as high on the RX pin. Additionally, it will still output 5V TTL serial signals on the TX pin, which could damage some 3.3V devices. To get around these problems, you might consider using a logic level shifter.