| Acroname Serial Standard |
Last Modified: 2006-07-21
For many years people have been championing the doom of RS-232 serial ports on computers. While these are not currently as popular for high-volume consumer applications, they remain the most consistent standard for simple peripheral, communication, and Unix console interfaces.
In the robotics community, they are essential for communicating with various controllers, devices, and sensors. In many of these cases, the data rate is not very fast and the distance traveled in the wire can be minimal. In many cases, the signals are converted from TTL levels to RS-232 levels and then immediately converted back to TTL levels at the other end of a small length of wire. This increases cost, board real estate, and power consumption for no good reason.
The Acroname Serial Standard is actually a TTL level UART interconnect standard. By specifying this at the TTL level, the devices can be directly plugged together where needed. In the case where RS-232 levels are needed, a small connector assembly can be used.
Separating the communications connection from the line levels offers some distinct advantages such as new protocol incorporation, quick interfacing and physical modularity.
New protocols are constantly being introduced that can constrain hardware design choices when building a system. Using the standard can allow serial protocol bridging to 802.11b/g, USB, RS-232, Bluetooth and others. Interfacing technology can improve and change with new effort only necessary in creating bridging interfaces once the serial standard is adopted.
The interconnect modularity creates the potential for quickly interfacing to controller serial ports for quick debugging access. A number of different interface connectors adhering to the standard can easily interface to the controller serial port.
As an example, setting configuration parameters for a XScale processor can be accomplished through issuing commands to a serial port. More specifically, an example parameter change may be Ethernet connection configuration for the XScale. Stubbing a XScale serial port into a serial standard allows easy access with a standard compliant serial interface connector. After the configuration changes are made through the XScale serial port, the interface connector could be removed once the system is up and running.
Finally, since the Acroname serial interface connector contains a DB-9 connector and adheres to the serial standard, packaging a design into a case need not contend with the absolute orientation of the board in the enclosure. A small extender cable can route the serial to the optimal spot in the enclosure without the DB-9 connector location dictating the board orientation.
Acroname has standardized on the following interconnect scheme for the serial interface standard. This standard offers some minimal power distribution for line drivers. All BrainStem modules use this standard. This allows easy switching of the BrainStem network's router without bloating the boards and wasting the line drivers and DB-9 shells on boards that are not routing or multiplexing serial communications.
All BrainStem modules use this standard with one headers on each module. The interconnect Acroname uses is a Samtec part (#TSW-104-08-G-S-RA). These are right angle headers to allow tight board stacking of modules but they need not be right angle.
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