Hi,
I'm working on a project to man-in-the-middle a half-duplex serial bus (where tx and rx share a wire) between some Intel 8031 microcontrollers in an old IBM wheelwriter typewriter. Generally, the project is to intercept bytes coming from the keyboard controller, decode and send them to a serial port to an external computer, receive bytes from the external computer, and re-encode and send them to the motor-driver part of the typewriter. The protocol involves sending some bytes, and having them ACK'd (mostly by an all-zero response). According to my logic analyzer, the data appears to be using the so-called mode 2 of the 8031 uart, where a ninth bit is used to indicate whether the 8 preceeding bits are an address of a slave microcontroller. I read that the teensy 3.5 supports a 9-bit mode that would seem to be compatible, but the bit rate the typewriter is using is something around 190k, not one of the standard ones. To complete the man-in-the-middle, I'm wanting three UARTs, one to talk to the keyboard controller, one to talk to the motor-driver board (both talking 190k 9n1), and one (115200 8n1) to talk to the external computer.
What am I going to need to do to support the weird baud rate and a normal one at the same time?
I'm working on a project to man-in-the-middle a half-duplex serial bus (where tx and rx share a wire) between some Intel 8031 microcontrollers in an old IBM wheelwriter typewriter. Generally, the project is to intercept bytes coming from the keyboard controller, decode and send them to a serial port to an external computer, receive bytes from the external computer, and re-encode and send them to the motor-driver part of the typewriter. The protocol involves sending some bytes, and having them ACK'd (mostly by an all-zero response). According to my logic analyzer, the data appears to be using the so-called mode 2 of the 8031 uart, where a ninth bit is used to indicate whether the 8 preceeding bits are an address of a slave microcontroller. I read that the teensy 3.5 supports a 9-bit mode that would seem to be compatible, but the bit rate the typewriter is using is something around 190k, not one of the standard ones. To complete the man-in-the-middle, I'm wanting three UARTs, one to talk to the keyboard controller, one to talk to the motor-driver board (both talking 190k 9n1), and one (115200 8n1) to talk to the external computer.
What am I going to need to do to support the weird baud rate and a normal one at the same time?