On Thursday, April 07, 2016 3:16 AM, Ian Abbott wrote: > On 06/04/16 19:06, H Hartley Sweeten wrote: >> The "hc" type boards have 64 analog input channels with a 64 entry queue. >> All the others have 16 channels and a 256 entry queue. >> >> Currently the boardinfo 'qram_len' is used to initialize the subdevice >> 'n_chan' and 'len_chanlist'. This works for the 64 channel boards but >> sets the 'n_chan' wrong for the 16 channel boards. > > I think the 256 QRAM positions is to allow use with a set of EXP-1800 > boards, each of which can multiplex one of the single-ended inputs of > the DAS-1800 series into 16 channels. According to the user's guide, > they can be daisy chained to provide up to 256 channels. > > Datasheet: > > http://www.tek.com/sites/tek.com/files/media/media/resources/exp-1800_ds.pdf > > User's Guide download page (need to fill in contact info!): > > http://www.tek.com/manual/exp-1800-users-guide-92160b-manual > > > So it's probably best to leave the number of channels alone. I wasn't aware of the EXP-1800 expansion board. I get a 403 Forbidden error when I try to download the user's guide. Do you have a copy you can send to me? The EXP-1800 support looks like it will need additional changes to the driver in order to work correctly. According to the data sheet: 1) all board input channels must be configured as single-ended, EXP-1800 inputs can be single-ended or differential. Not sure how the board needs to be programmed to achieve this. 2) only gains of 1 and 50 are selectable on a per-channel basis 3) resolution is 12-bit, not clear how this works on a 16-bit board 4) max ai speed depends on the EXP-1800 gain not the board gain 1 = 312kHz sample rate gain 50 = 150kHz sample rate 5) gain must be the same on all channels and the boards gain must be 1 Additionally, it's not clear how the channel mapping works for each EXP-1800 connected to a board input channel. I think it's better to set the number of channels to 16 and just support the on-board analog inputs for now. Once the EXP-1800 support is figured out it can be added. Regards, Hartley _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
