Rockbox Technical Forums

Rockbox Development => Starting Development and Compiling => Topic started by: taksato on September 22, 2017, 05:03:16 PM

Title: Further research on im413 sanssa dock
Post by: taksato on September 22, 2017, 05:03:16 PM
After reading here and the two source links below the data cable table I decided to have another go at trying to get at the protocol between im413 dock and sansa e200 series v2.

Wired up pins 24 and 25, pin 26 is ground verified via multimeter. Tapped gnd at an easier location. Wrote a pc tool to open two com ports, listen, output to stout and optionally a file also. The output is srcport,  timestamp, and each byte in he'd. Serial adapters level shift to 3.3v.

Closed the back of the sansa to make battery sturdy. Plugged into im413, wired common ground to both serial adapters, wired pin 24 to one rx, wired 25 to the other rx, and plugged sansa into dock to turn it on.

Ran my pc program, started a playlist on sansa, mashed buttons which provide commands to sansa not only dock.  Result was no outputs on either presumed serial line. Tried again by listening to serial ports before sansa went on. Nothing.

Disassemble part of im413 and inspected connector. Hmmmm, these pins don't seem to be connected. No wonder no serial. C200 series also seem to lack connection  these pins.

On the anything but site someone observed pin8 volts at 3.3v when buttons on remote are touched.

Open sansa again and bring pin 8 out. Close the back. Putin battery. Put in dock. Test remote to dbl check no short.  Works.  Connect gnd to gnd on serial adapter and pin8 to rx. Fire up a terminal. Observe led on rx is continuously on or blinking too fast to observe breaks. No data shown on terminal. Open my hex output program to see if any raw or terminal invisible dats is  coming.  Nope, nothing.

Press player directed buttons on the remote. Strange. Dock lights up so command received. No action on player. Repeatable 100%. Unplug serial adapter leaving pin engages results in player directed commands working again.

Our wiki says pin 8 is a line out of audio, so I pressed the connector against an audio line on earphones and had volume at 100, but observed no sounds. Expected faint sound. I still think it is part of the interface for dock to player commands.

Based on dock pin connections, e200 pins,  c200 pins, these forums discussed in wiki,  the wiki, and my observations... have formed a few new theories.

1. I need a resistor on pin8,so I don't get the dock or player mad at me.  Any recommended values?
2. Protocol isn't serial and need a scope to see signals.
3. USB d/d pins get used as serial lines when the dock mode resistance is detected.

Any comments please?