Main Site Documentation

SD Reader Mode Signals


#1

The only issues I’m having with the SD Reader Mode is the U1_Connect signal and what I should be expecting from the read register command (J). The actual functionality is working great.

Prior to connecting the board to the computer but after successfully sending the initialize SD Reader Mode command (I D:) I expect the U1_Connect pin (pin 58) to go high. This does not occur, the U1_Connect pin stays low. The device status register reads $81 which is expected.

After connecting the board to the computer, I expect the U1_Connect pin to go low and the status register to read $C9. U1_Connect pin is low because it never changed to begin with and the status register reads $C1 (not expected).

I eject the device from my computer without unplugging the USB and nothing changes from the previous signal and register.

I then unplug the USB from the computer and the U1_Connect pin is still low and the status register is back to $81.

Is there a reason why the U1_Connect pin isn’t changing? I’m communicating in SPI mode so I’m using pin 58 as the U1_Connect pin. Also, shouldn’t I expect bit 3 (U1 mounted/unmounted) on the status register to toggle?

Thanks for the help.


#2

@ Mike Williams -

if you are using ALFAT-SDR board, it means HS PHY is installed and you should use “I D:H”.

This pin is only high when ALFAT is in SD reader mode and “connected” to PC. “Connected” here means PC and ALFAT can talk together, not only plug the cable in.

The status is 0x81 it means ALFAT is in SD reader mode, but bit 6th is 0, this one should be 1 then the signal will work as you expected.

This bit is only for USB Host, while we are in USB Device (SD reader), this bit won’t tell you any thing.