DAC and ADC delays not accounted for correctly in BioSigRP

Tech Note: TN0221
Product: BioSigRP
Version: All
Date Added: 2006-09-22


Devices such as the RP2, RX6 and RX8 uses Sigma-Delta D/A and A/D to ensure high quality signal conversion. However, the high bandwidth low distortion characteristics associated with Sigma-Delta converters comes at the cost of DAC and ADC delays. These delays must be accounted for to ensure accurate timing of stimulus and recording. Currently, BioSigRP automatically detects the hardware and, if the device is an RP2.1, corrects for these delays. However, BioSigRP also applies the RP2.1 known delay information to the RP2 and does not auto- correct for any other devices.


For the RP2, since the incorrect delay is implemented (longer than required), delay your SigGen signal by one millisecond by modifying the start time of your signal segments. For example, if your signal contains one segment, set the start time of the segment to 1 msec. For consistency, also increase the length of the signal by 1 millisecond.

For other devices, Use the table below to find the delay associated with your device, then use the TTLDelay2 component in your circuit to implements delays based on a user-defined number of samples.

Device DAC Delay ADC Delay
RP2.1 30 samples 65 samples
RA16BA 18 samples NA
RM1/RM2 17 samples 16 samples
RX6 43 samples 70 samples
RX8 23 samples 47 samples