What is uLan
uLan provides a 9-bit message-oriented communication protocol, which is transferred over an RS-485 link. Characters are transferred the same way as for RS-232 asynchronous transfer except for the parity bit, which is used to distinguish between data characters and protocol control information. A physical layer consists of one twisted pair of leads and RS-485 transceivers.
The use of a 9-bit character simplifies the transfer of binary data and, for intelligent controllers, can lower the CPU load because the CPU does not need to care about data characters sent to other nodes. Producers of most microcontrollers for embedded applications know that and have implemented 9-bit extensions in UARTs of most of today's MCUs. There is the list below to mention some of them:
- many ARM based MCUs and SOCs (NXP LPC 17xx, 4xxx, iMX6, iMX8, imxRT, Microchip SAMv7, STM ...)
- members of Motorola 683xx family ( 68332, 68376, ... )
- Hitachi H8S microcontrollers
- all Intel 8051 and 8096 based MCUs with UART
Intel developed a multiprotocol UART i82510 already in the eighties, which is very well suited for implementing a 9-bit communication interface for PC computers. The second example of the chip, which is well suited for 9-bit communication, is OX16C954-PCI, produced by Oxford Semiconductors.
One of the problems is that a 9-bit communication is missing standardization of message protocol. Drivers and formats of one possible implementation of the uLan message protocol are provided by this project for GNU/Linux, Windows, NuttX, and embedded devices. A broad range of interfaces is supported, USB converters, PCI cards, SoC, and embedded UARTs. All from the single source tree.