On Sun, Apr 8, 2018 at 5:01 PM, Ethan Dicks <ethan.di...@gmail.com> wrote: > On Sun, Mar 25, 2018 at 3:48 PM, Ethan Dicks <ethan.di...@gmail.com> wrote: >> SN-921 >> >> https://upload.wikimedia.org/wikipedia/commons/7/74/Sgi_dialbox_sn-921_front.jpg > >>>>> https://github.com/hanshuebner/sgi-dialbox-usb/blob/master/dialbox.py >> >> I'm going to test this code out when I have a dialbox in hand. > > I have now tried this and am not having success. I have a traffic > light on the serial cable and I know I'm getting chars out of the host > and that I don't have TxD and RxD swapped. I'm not seeing any > responses from the dial box and the python script does all the > initialization and just sits there. Frobbing the knobs produces no > blinks on the traffic light and no text from the script.
OK. I got the script working and two things were impediments: 1) One of the SN-921 pinouts running around on the 'net is incorrect, as I posted. The *correct* place for the ground is DE-9 pin 7. I was apparently getting enough of a parasitic ground to get chars *from* the SN-921 but not *into* the SN-921. As it turns out, it appears the SN-921 as set up for the SGI is mute except for a single status success byte 0x20. If you send it an INIT command (also 0x20), it will respond with its success after a fraction of a second, which leads to another problem... 2) The python script dialbox.py slams the init code and a command to set the dials to auto-report all at once, before the SN-921 has a chance to initialize. So to fix that, I added a few extra lines to send the 0x20 INIT command, pause, check for a 0x20 response (INIT GOOD) _then_ send the AUTO command (0x50 0x00 0xFF), which sets all 8 dials (one bit per dial) to send back a 3-byte packet when twisted. With the custom serial cable fixed and the init sequence fixed in the Python script, I'm now getting the right data stream when I twist any of the knobs. I did get a copy of dialbox.c from http://www.geocities.ws/joekrahn/dialbox.tgz Jim Stephens tracked down that there was a massive GeoCities scan done in 2009 and the file I was looking for happened to be scooped up then. There are a number of dial box and button box command sets in that code which reveals some of the more complex behavior possible. Here's a slice of the command byte definitions... #define DIAL_INITIALIZE 0x20 #define DIAL_SET_AUTO_DIALS 0x50 #define DIAL_SET_AUTO_DELTA_DIALS 0x51 #define DIAL_SET_FILTER 0x53 #define DIAL_SET_TEXT 0x61 #define DIAL_SET_BUTTONS_MOM_TYPE 0x71 #define DIAL_SET_AUTO_MOM_BUTTONS 0x73 #define DIAL_SET_LEDS 0x75 #define DIAL_SET_ALL_LEDS 0x4b It should be possible to write up a protocol definition from studying the code. I do not have one of these button boxes so I can't validate its behavior. -ethan
