When setting up the serial connection I discovered something really strange. I first tried to use a BusPirate and TP13 (
https://d3nevzfk7ii3be.cloudfront.ne...FsMJPmbvPLmRZs - Top right) as the 1V8 reference but I was only able to receive data. I then tried one of these cheapo UART/USB converter in combination with a logic level converter. Same problem here. I got it working by applying 3V3 on the Kindle. Has anybody else had that problem? I have never seen this behavior on any embedded system.