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SigmaStudio programmer coexistence

JP150PCB 1.3PCB 1.4since 26.8.0Jan PřibyslavskýThis page does not apply to the product or PCB revision chosen in the header.

A SigmaStudio USBi programmer on the DSP I2C connector is a second master on the bus the firmware uses to talk to the DSP. The firmware detects it within milliseconds and stands down until it has finished, so a DSP download or live tuning can be done on a running module without any preparation.

How it works

The firmware samples the bus lines at 10 kHz and, on traffic it did not originate, suspends its own periodic DSP access for 750 ms after the last foreign transaction, re-arming as long as the programmer remains active. While a programmer is active:

  • the level meter freezes on its last reading, because the firmware is not reading the DSP;
  • automatic power-down is suspended, so a tuning session is never interrupted;
  • mute, reset and fault clearing stay available.

A bus held low for more than 3 s is reported separately as a stuck bus (a wiring or hardware fault), and the programmer indication is cleared while a stuck bus is present. MuraLink shows External programmer in the strip above its DSP pages while one is active and greys out the controls that use the bus; over the control interface the read-only queries SYS:I2C:GUARD?, SYS:I2C:GUARD:COUNT? and SYS:I2C:GUARD:STUCK? report the state, the number of episodes and a stuck bus (SYS:I2C:GUARD reference).

Which bus

The DSP has its own bus. The programmer never shares a bus with the power stages, the temperature sensor or the settings memory, so volume changes and measurements continue during a session.

The DSP shares the system bus with the power stages, the temperature sensor and the settings memory. During a session the firmware's own traffic on that bus pauses.

Known issue

After a SigmaStudio session on PCB 1.4 the guard can stay active until the module is reset, even with the USBi unplugged; DSP queries then answer ERROR and input or power-mode changes do not reach the DSP. Reset or power-cycle the module after using the USBi. See Known issues.