diff --git a/README.md b/README.md
index 9f6826b..becf74d 100644
--- a/README.md
+++ b/README.md
@@ -15,9 +15,8 @@ Also, Python codes are provided for the calibration of the Spherical Microphone
 
 # opensCAD designs
 The designs are in the `cad` folder:
-- `sma_open.scad` for open SMA configuration with cylindrical shaped microphones,
-- `sma_rigid.scad` for rigid SMA configuration with cylindrical shaped microphones,
-- `sma_rigid_mchstreamer.scad` for rigid SMA configuration with digital MEMS microphone and embedded USB sound card.
+- `sma_open.scad` for open SMA configuration,
+- `sma_rigid.scad` for rigid SMA configuration,
 
 Examples of SMA configurations are provide in `.json` files.
 See the documentation in `.scad` files to create or customize a SMA design.
diff --git a/cad/sma_rigid.scad b/cad/sma_rigid.scad
index 1dc19ba..3984e38 100644
--- a/cad/sma_rigid.scad
+++ b/cad/sma_rigid.scad
@@ -1,10 +1,8 @@
 /*
- * Rigid SMA design for cylindrical microphone capsules
+ * Rigid SMA design
  * Copyright 2023 Pierre Lecomte - sekisushai@gmail.com
  */
 
-include <threads.scad>
-
 /*
 The rigid SMA is composed of two hemispherical shells to render separately for 3D printing.
 */
@@ -19,7 +17,7 @@ res = 32;
 
 /*[ Array parameters ]*/
 // sphere radius (mm):
-r = 60;
+r = 80;
 
 // shell thickness (mm):
 e = 6;
@@ -30,6 +28,12 @@ theta = [0, 90, 90, 90, 90, 180, 54.7356, 54.7356, 54.7356, 54.7356, 125.264, 12
 // microphone azimuth coordinates (°):
 phi = [0, 0, 90, 180, 270, 0, 45, 135, 225, 315, 45, 135, 225, 315];
 
+// microphone type
+mic_type = "1/4"; // [1/4:Quarter_Inch, PDM:PDM MEMS]
+
+// include USB sound card (only for digital MEMS mics)
+usb_card = true;
+
 /* the microphone array can be rotated to be in accordance with the array cut and mic stand position
 */
 // microphones global rotation (°):
@@ -69,6 +73,7 @@ The mic stand threaded hole should be close to the passing cable hole. It's dire
 dir_thread = [13, 0];
 
 // DO NOT EDIT BELOW HERE
+include <threads.scad>
 
 // Hollow sphere
 module hollow(r1=r-e, r2=r, fn1=$fn, fn2=$fn){
@@ -78,8 +83,7 @@ module hollow(r1=r-e, r2=r, fn1=$fn, fn2=$fn){
     }
 }
 
-// Torus for "joint torique" for B&K 1/4" mics
-
+// Torus for O-ring for 1/4" mics
 module b_k(){
 mirror([0,0,-1])
 rotate_extrude($fn=32){
@@ -91,12 +95,69 @@ square([3.55, 1.1*e]);
 }
 }
 
-module mics(){
+// Adafruit PDM MEMS breakout. 
+// https://www.adafruit.com/product/3492
+module pdm_breakout(l=14-5, w=13-5){
+$fn=64;
+
+translate([-l/2,-w/2,-5]){
+
+// big condo
+linear_extrude(7){
+translate([l/2+4.5,w/2,0])
+square([3,4],center=true);
+}
+
+// small condo
+linear_extrude(5.75){
+translate([l/2+2.75,w/2,0])
+square([3,4],center=true);
+}
+
+// tiny resistor
+linear_extrude(5.5){
+translate([l/2-2.9,w/2+1,0])
+square([3,2],center=true);
+}
+
+// mic
+linear_extrude(6){
+translate([l/2,w/2-0.5,0])
+square([3.5,4.5],center=true);
+}
+linear_extrude(50){
+translate([l/2,w/2,0])
+circle(d=2);
+}
+
+
+// wires
+translate([0,0,5])
+linear_extrude(2){
+translate([l/2,w,0])
+square([l+4,2.5],center=true);
+}
+
+linear_extrude(5){
+difference(){
+minkowski(){
+square([l,w]);
+circle(2.6);
+}
+}
+}
+}
+}
+
+module mics(type){
         rotate(mics_rotate)
 for (i = [0 : len(theta)-1]){
     rotate([theta[i], 0, phi[i]])
     translate([0, 0, r-e+1]){
+        if (type=="1/4")
     b_k();
+        else 
+    pdm_breakout();
     translate([3,3,e-1.8])
         linear_extrude(3)
     text(str(i+1), size=3);
@@ -104,6 +165,45 @@ for (i = [0 : len(theta)-1]){
 }
 }
 
+module mchstreamer(){
+    $fn=64;
+    adj = 0.2; // adjustment
+    // usb_cart dimensions
+    w_usb = 40+adj;
+    l_usb = 60+adj;
+    h_usb = 15+adj;
+    attach_l = 20;
+    attach_w = 7.3 + adj;
+    attach_h = 8.2+adj;
+    rotate([0,-90,90])
+    translate([r-l_usb-attach_l/2,-w_usb/2,-h_usb/2])
+    union(){
+    cube(size = [l_usb, w_usb, h_usb], center = false);
+        plug_l = 20;
+        plug_w = 12+adj;
+        plug_h = 10.7+adj;
+        translate([l_usb - plug_l/2, w_usb/2 - plug_w/2, 1.8+adj])
+        cube(size = [1.5*plug_l, plug_w, plug_h], center =false);
+        translate([l_usb - attach_l + 2, 1, 2.4+adj])
+        attach();
+        translate([l_usb - attach_l + 2, w_usb - attach_h -1, 2.4+adj])
+        attach();
+        translate([w_usb + 2, 0, 0])
+        cube(size=[attach_l, w_usb, 2.7]);
+     
+    }
+    module attach(){
+
+    rotate([0, 90, 0]){
+        translate([-attach_w/2, attach_h/2, attach_l/2]){
+union(){
+        cube(size=[attach_w, attach_h, attach_l], center = true);
+        cylinder(r=1.5, h=2*attach_l );
+    }
+    }}
+}
+}
+
 module bottom_shell(r1= r-e, r2=r-e/2, r3=r, delta=0.2) {
     union(){
     difference(){
@@ -155,8 +255,12 @@ cylinder(d=param[1]+0.2, h=param[0]+1, $fn=6);
 }
 
 module attach() {
-rotate([(angle_min+angle_max)/2,0,hole_phi_offset])
+rotate([(angle_min+angle_max)/2,0,hole_phi_offset]){
+if (usb_card==false)
 cylinder(d=d_hole, h=100);
+else
+mchstreamer();
+    }
 rotate([(angle_min+angle_max)/2 + dir_thread[0],0, hole_phi_offset + dir_thread[1]])
 translate([0,0,(r-3*e)])
 render()
@@ -181,7 +285,7 @@ difference(){
 bottom_shell();
 attach();
 vis_all();
-mics(); 
+mics(mic_type); 
 }
 }
 
@@ -189,7 +293,7 @@ module top_shell_all(){
 difference(){
 top_shell();
 attach();
-mics();
+mics(mic_type);
 vis_all();
 }
 }