Add some notes to README

README.md

@@ -10,3 +10,36 @@
 *   13: Top relay (L1)
 *   4: Middle relay (L2)
 *   15: Bottom relay (L3)
+
+
+## Notes
+
+### Using GPIO 1,3
+
+If your device uses the GPIO pins 1 (serial0 TX) or 3 (serial0 RX)for channels,
+you need to disable logging via the serial port:
+
+```
+mos config-set debug.stderr_uart=-1 debug.stdout_uart=-1
+```
+
+### Using ESP8285 or 1MB ESP8266
+
+You need to flash with the following statement in `mos.yml`:
+
+```
+build_vars:
+  FLASH_SIZE: 1048576
+```
+
+Note: OTA will not work on these devices, for lack of flash space for the
+alternate boot partition.
+
+### Using Sonoff-4CH
+
+Sonoff 4CH uses a bunch of GPIO pins for the LEDs and pushbuttons, and as such
+has no space for sensors.
+
+```
+mos config-set app.config=sonoff-4ch.json sensors.dht_gpio=""
+```