DAC and ADC delays not accounted for correctly in BioSigRP
Tech Note: TN0221
Product: BioSigRP
Version: All
Date Added: 2006-09-22
Issue
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.
Workaround
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.