Hello,
I have a project involving two serial devices and one USART. One device only receives and the other, EM-406a only transmits.
From what I read, the EM-406a should spit out nema data at 4800baund without any configuration.
The other device, serial LCD, never needs to transmit, just receive data for display.
Could I hooked the EM-406a to the MCU RX line and the LCD to the MCU TX line, provided they both run at 4800Baud?
I know a MUX could accomplish my goal, but the less circuity the better.
Thank you.
hi slagment
I’m no expert, but I would think this is perfectly possible.
Each stream doesn’t require any confirmation, plus the interrupts (on the AVR atleast) are separate for Send and Receive.
You don’t mention what uC you are using, but I know that Arduino has a Usart software library which allows other pins to be used.
Mike
Thanks,
Did more checking and found people who do this for many projects. I just need to make sure the serial settings will work for each device.
I will go a step further, but it may turn the stomach of some purists…
If your device isn’t moving at a high rate of speed and the other device you want to share with is only occasionally updated, you can even share the port with something that is at a different speed. In other words, if your LCD is on a serail backpack running at 115k, you can change the baud rate to spit out data to it and then change it back to continue receiving. It will likely trash one sentence of NMEA data, but TinyGPS and most posted samples are tolerant of that. I am absolutely not suggesting that this is a good design. But the SparkFun serial graphic LCD has a bad habit of reverting to 115k out of the blue, so to run it at a different baud rate reliably you have to do the handshake to get it to 115k during initialization and then set it to the baud rate you want. Most of the time that is unnecessary, but if you don’t do it every time, the LCD device becomes unusable if it ever does reset.
Yeah, the buggy serial Lcd has changed baud rate a few times. Twice it cut the back-light making the display un-readable. Adding some delays, and filtering out any command words helped.
I have to PCB this project, and really wanted a single sided board. Sharing the USART made routing easy.
Yeah, the LCD has its bugs, but once you have demonstrated that you can do some graphics at that price point, you are kind of stuck with it unless you can spare the ports and memory for a parallel and its library. I assume congrats are in order - failures usually don’t go to PCB.