An extended version of the CALICE silicon–tungsten ECAL, with 15 active layers, was tested in November 2021 at the DESY beam test facility. Respectively with the previous design, it featured some complete layers with a thin PCB design, and a new compact DAQ handling 15 layers in a common set. The noise, self-trigger performance and response to punch-though electrons, without tungsten absorbers, was evaluated for each of the 15,360 channels, using an improved procedure. Showers of low-energy electrons (1 to 5 GeV) have been recorded in two configuration of absorber, and are being analysed. Some preliminary results will be shown here.