Problem: SPI Connection between two D1 (ESP8266) boards does not work properly, only master to slave transfers data correctly.
What I did: I connected two Wemos D1 R2 via SPI and installed the library from https://github.com/esp8266/Arduino. I connected MISO, MOSI, SCK, SS and ground 1:1. On one D1 I run SPISlaveTest on the other SPIMaster from the examples. The D1 are located directly beside each other, cables are only 15 cm long.
Effect: While the slave receives strings from the master fine the master seems to get crippeled answers from the slave, they appear as ??? and other characters. If I connect the slaves SS to +3.3V it reacts like expected: The slave receives no more, the master gets no reponses.
What I already tried:
- Updated the Libraries to the latest versions
- Changed delay to wait for answer
- tried SafeMaster.ino
- Changed D1 hardware on both sides
Everything unfortunately did not help.
Any tip is very appreciated.