As the TMC2208 uses a single pin for UART comms MCU<>TMC2208, I thought it was a waste using separate Rx/Tx pins on the MCU that combined via a 1k resistor anyway.
So I've made a very small change to Arduino's SoftwareSerial module to allow the use of a single Rx/Tx pin .. this freed up the Tx pins on the mega's that were being used for my TMC2208's.
I'll do a 32-bit STM32F4 version of SoftwareSerial at some point soon too.
All you do is replace Arduino's two SoftwareSerial files with these, then you can set the Rx & Tx pins in your Marlin pins config file to be the same pin, the modified SoftwareSerial will do the rest.
NB .. The single Rx/Tx pin needs to have PCINT capability, which was the Rx pins I was using anyway.
You would have too move your 1k resistors that you have between your MCU Rx & Tx pins and place it from the new single Rx/TX pin (your old Rx pin) to +5V (simple pull-up) .. though the resistor may not be needed at all so could be removed depending on with TMC2008 driver board being used.
The two SoftwareSerial library files (SoftwareSerial.cpp & SoftwareSerial.h) on my system are here ..
C:\Program Files (x86)\Arduino\hardware\arduino\avr\libraries\SoftwareSerial\src\SoftwareSerial.cpp
C:\Program Files (x86)\Arduino\hardware\arduino\avr\libraries\SoftwareSerial\src\SoftwareSerial.h
They are the ones you replace with these modified ones - if you so wish.
So for me, I've gone from this ..
#define X_SERIAL_TX_PIN 40
#define X_SERIAL_RX_PIN 63
#define X2_SERIAL_TX_PIN -1
#define X2_SERIAL_RX_PIN -1
#define Y_SERIAL_TX_PIN 59
#define Y_SERIAL_RX_PIN 64
#define Y2_SERIAL_TX_PIN -1
#define Y2_SERIAL_RX_PIN -1
#define Z_SERIAL_TX_PIN 44
#define Z_SERIAL_RX_PIN 66
#define Z2_SERIAL_TX_PIN 42
#define Z2_SERIAL_RX_PIN 65
#define E0_SERIAL_TX_PIN -1
#define E0_SERIAL_RX_PIN -1
#define E1_SERIAL_TX_PIN -1
#define E1_SERIAL_RX_PIN -1
#define E2_SERIAL_TX_PIN -1
#define E2_SERIAL_RX_PIN -1
#define E3_SERIAL_TX_PIN -1
#define E3_SERIAL_RX_PIN -1
#define E4_SERIAL_TX_PIN -1
#define E4_SERIAL_RX_PIN -1
to this ..
#define X_SERIAL_TX_PIN 63
#define X_SERIAL_RX_PIN 63
#define X2_SERIAL_TX_PIN -1
#define X2_SERIAL_RX_PIN -1
#define Y_SERIAL_TX_PIN 64
#define Y_SERIAL_RX_PIN 64
#define Y2_SERIAL_TX_PIN -1
#define Y2_SERIAL_RX_PIN -1
#define Z_SERIAL_TX_PIN 66
#define Z_SERIAL_RX_PIN 66
#define Z2_SERIAL_TX_PIN 65
#define Z2_SERIAL_RX_PIN 65
#define E0_SERIAL_TX_PIN -1
#define E0_SERIAL_RX_PIN -1
#define E1_SERIAL_TX_PIN -1
#define E1_SERIAL_RX_PIN -1
#define E2_SERIAL_TX_PIN -1
#define E2_SERIAL_RX_PIN -1
#define E3_SERIAL_TX_PIN -1
#define E3_SERIAL_RX_PIN -1
#define E4_SERIAL_TX_PIN -1
#define E4_SERIAL_RX_PIN -1
So I've gained back 4 wasted pins (the old Tx pins) to use for whatever I wish.
I've done this using Marlin bugfix-2.0.x, I've not yet tried it with Marlin bugfix-1.1.x.
Edited 2 time(s). Last edit at 03/08/2019 10:13AM by Pippy.
