[EXT_EP-9789] ADCBuf causes jitter when switching clock sources Created: 06/May/20 Updated: 25/Mar/25 |
|
| Status: | Accepted |
| Project: | Embedded Software & Tools |
| Component/s: | None |
| Affects Version/s: | None |
| Fix Version/s: | None |
| Type: | Bug | Priority: | Medium |
| Reporter: | TI User | Assignee: | TI User |
| Resolution: | Unresolved | Votes: | 0 |
| Remaining Estimate: | Not Specified | ||
| Time Spent: | Not Specified | ||
| Original Estimate: | Not Specified | ||
| Product: | TI Device Drivers |
| Internal ID: | TIDRIVERS-4127 |
| Found In Release: | TIDRIVERS_5_10_00 |
| Fix In Release: | TIDRIVERS_5_20_00 |
| Affected Platform/Device: | CC13x2 CC26x2 CC13x2x7 CC26x2x7 CC13x4 CC26x3 CC26x4 |
| Workaround: | Two Workarounds
1. Use asynchronous sampling mode at the cost of a slightly corrupted sample because the sampling timing is slightly shifted 2. Ensure that no clock switches take place while using the ADCBuf (always run on XOSC_HF while ADCBuf active) |
| Description |
|
At the maximum sampling rate of 200 kHz, CC26X2 devices have 120 clock cycles at 120 MHz to perform the ADC conversion. The hardware requires 118 clock cycles to perform the ADC conversion. Clock switching from XOSC_HF to RCOSC_HF, and vice-versa, consumes two clock periods. During clock source switching, using the TI Power driver, the ADC will run off a different clock source than the timer that generates the ADC triggers for a while. This is a problem, because the clock switch itself uses the whole time margin, so there is no margin left for any rate differences between the XOSC and the RCOSC. The next trigger as a result may be generated while a conversion is ongoing and thus do nothing. |