CF Meter
CF METER: main parameter page.
A probe. It measures, on the unit, how long the ColdFire's frame interrupt takes and how much time main's idle loop gets (with CF Meter Idle), and, on core 0, how long the DSP waits for each frame, whether the ESAI underran or overran, and the frame period. It prints the numbers as audio on track 8. It is the instrument for pricing ColdFire voice engines such as SYNTH MACHINE, and for reading the DSP's load during normal play.
Access
An effect on track 8 only: select T8, press FX2, and pick CF Meter.
T8's audio is replaced by the readout (its machine still runs). Not in an
official remix; build the test remix cfmeter. That image takes DARK REV
off the chooser, because the readout uses its DSP words. Hardware: cursory testing on Sam's MKII (owner report, 16 Oct 2026).
Operation
- Build and flash the test remix, then power-cycle. Make a new project
and load a silent 4 s
SYNTH.wavinto FLEX slot 1. - Put CF Meter on T8's FX2, with BURN and DBRN at 0.
- Connect USB. The readout is on USB audio, T8 on channels 15 and 16 (post-FX, pre-fader, so LEVL and MAIN do not matter).
- Record about 12 s per state, then decode the capture with
cfmeter.py. A cycle is 2 s and the decoder needs two of its sync edges, so a take is 6 s at least. - Read the ISR mean and max, not idle percentage: task-level work below the UI's priority reads as busy while the panel stays responsive.
- BURN, MEM, SRC, SPAN and DBRN are read on track 8 only.
- A late frame shows as slot 9 jumping by a whole frame's polls.
Parameters
| Page | Knob | Range | What it does |
|---|---|---|---|
| 1 | BURN | 0-127, default 0 | 2 us of busy-wait per step at the start of every frame interrupt |
| 1 | MEM | 0-127, default 0 | MEM KB read after the burn, timed into slot 7 |
| 1 | DBRN | 0-127, default 0 | 24 x DBRN DSP cycles per sample, burnt by the insert before its sample loop |
| 1 | SPAN | 0-127, default 0 | what slot 7 prints: BURN or the walk; the HC poll loops' time; the eDMA handler's time inside the frame interrupt; all of that handler's time |
| 1 | SRC | 0-127, default 0 | the region MEM walks: 0 cached SDRAM, 1 uncached alias, 2 on-chip SRAM |
Under the port, BURN 20 added 40.0 us to the interrupt mean (2 us x 20). The port's durations are its own clock's, not the unit's; the unit's numbers are not measured.
Screen Reference
CF METER: effect selection and setup parameters.
Status: on hardware: cursory testing on Sam's MKII (owner report, 16 Oct 2026); ColdFire half on image 92 (Sam's MKII, 3 Oct 2026: interrupt 123.1 us stopped, 213.5 us playing); the DSP slots and DBRN under the port only (4 Oct 2026).
Module facts (developers)
Probe: frame-interrupt duration and (with CF METER IDLE) idle time, plus core 0's frame spin count, ESAI underrun/overrun frames and frame period, printed as audio on T8's FX2.
| Detail | Value |
|---|---|
| Author | sambanks |
| Category | Reference |
| Kind | hybrid |
| Test status | on hardware: cursory testing on Sam's MKII (owner report, 16 Oct 2026); ColdFire half on image 92 (Sam's MKII, 3 Oct 2026: interrupt 123.1 us stopped, 213.5 us playing); the DSP slots and DBRN under the port only (4 Oct 2026) |
| FX2 ID | 0x0e |
| Parameters | BURN@0, MEM@1, DBRN@2, SPAN@4, SRC@5 |
| Included in | no official remix |
On GitHub: https://github.com/sambanks/octabam/blob/main/modules/cfmeter/README.md