Pro mini connected modules with SPI and rx/tx AND debugging/programming


I've got a pro mini and connect a SIM808 breakout via serial connection (rx/tx) and a LoRa breakout by SPI. In addition I'd like to use a seral monitor for debugging and a possibility for programming the MC.

By now I'm using a software serial für the Sim808 and a usb-TTL adapter for programming / serail monitor at the hardware serial port. But I'd like to avoid the software serial. Is that possible?

I read somewhere, that it's possible to connect the usb-ttl adapter to the same hardware serial pins as the SIM808 and by that are able to read at least the seriell outputs of the MC, but that sounds a bit "unstable" to me. And I understood I can't use that solution for programming.

Thanks for your advice!

Yes, trying to program over the same port you use for other devices is difficult. Someone on the forum posted a shield or addition to the board that can detect programming and switch between serial with USB/TTL chip and with the device you connect to, such as a sim device.

If you're comfortable programming your arduino over ICSP header with a second arduino, you can use that, which erases the bootloader to save additional 512 bytes of space for your program usage. This way you actually free the hardware serial port to use on your sim device.

This may help:

thanks for your response. Interesting approach, but additional hardware is not what I'm looking for. Instead I'm more and more considering alternatives to the pro mini with more UARTs and maybe more "power" as well.

For a single-board solution, you can check out Bobuino made by @CrossRoads

The board is based off ATMEGA1284P with 128KB FLASH, 16KB SRAM, and 2 hardware serial ports, also 32 GPIO pins.

The closest to the form factor of the ProMini are the Arduino Micro and the SparkFun ProMicro; both provide a serial port that is independent of the USB connectivity. There are also Teensies that are quite small; those are far more powerful; I'm not familiar with them but it's my understanding that a number of pins can be configured as UART if they are based on certain processors.

What was the motivation to use a ProMini? Size? Low power?

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