First time posting here. I have an F20-uSD module and have been talking with it using a PC. All is going pretty well now with the exception of one point I will discuss in a moment.
I should mention initially that having had no previous experience with an ALFAT, reading the ALFAT manual to learn how to talk with the F20 proved a challenge. I eventually threw up my hands, copied the text of the ALFAT manual, and edited out the text of all features that are reportedly not supported in the F20. After some further cleanup, I have a document that seems pretty close to what I need without having to wade through a lot of useless info. By the way, one detail that is omitted in the F20 Developer’s Guide is that, while it does say there are only 2 file-handles available, it does not say that they must be identified as 0 and 1. File-handles 2 through F are not available in the F20.
Also, based on the ALFAT feature where grounding the SPI_SCK pin during reset or power up causes the ALFAT’s baud rate to default to 9600, I was hoping that a similar feature was available in the F20. Experimentation has shown that it does not seem to be available on the F20 regardless of which pin is pulled low and it always defaults to 115200 baud.
There does seem to be a bug in the F20 firmware where it does not comply with the ALFAT design. It concerns the use of the N command used to fetch successive directory entries after being initialized with an @ command. According to the ALFAT documentation, after the last directory entry has been processed, the next N command should cause the F20 to return !04 which indicates that the end of the file/folder list has been reached. This is not considered an error.
However, when the F20 reaches the end of the file/folder list, instead of !04 it invariably returns !03 (Operation Failed) which really is classified as an error.
The firmware in my F20 is version 0.5.0
I can program around that for the moment but if the firmware is likely to be updated to correct this, it would be nice to know this change is coming in the future.