add bom

bass boost (B) and treble boost (T)

BOM.csv

@@ -0,0 +1,13 @@
+Quantity,Manufacture Part Number,Manufacturer,Description,LCSC Part Number,Package
+1,STM32F103C8,STM,Microcontroller ,,
+1,SMD-5032_4P8M20pf20ppm,Zhejang Abel Elec,8Mhz Crystal,C133333,SMD-5032
+1,DC-470-2.1GP,GANGYUAN,GANGYUAN DC-470-2.1GP ,C194407,
+6,XKB5858-W-TP,XKB Enterprise,XKB Enterprise XKB5858-W-TP ,C381091,
+4,WF06Q1002BTL,Walsn Tech Corp,10k 0603 Resistor,C305259,SMD0603
+2,EWH1HM4R7D11OT,Aihua Group,4u7 leaded cap ,C105327,radial_D5P2
+2,ECSS05072R2M101P00,Guangdong TOPAZ Elec Tech,2u2 leaded cap,C156723,radial_D5P2
+12,PE105J2A0501,KYET,1u Polyester film cap,C390180,rectangular_7x5P5
+2,0603CG200J201NT,Guangdong Fenghua Advanced Tech,20pF crystal cap,C63680,SMD0603
+2,0603X106K160NT,Guangdong Fenghua Advanced Tech,10u cap,C70225,SMD0603
+7,D-G080508G1-KS2,Wuxi ARK Tech Elec,LED bright green,C107402,SMD0805
+1,TSA061G50-250,BRIGHT,switch ,C294501,THT

README.md

@@ -1,27 +1,32 @@
-## Wat
+![render image](doc/images/render.png)
 
-This pcb is an audio multiplexer, meaning it can switch three analog inputs into one analog output. 
+<iframe src="https://myhub.autodesk360.com/ue28af833/shares/public/SH56a43QTfd62c1cd96847154d5ed1f7a373?mode=embed" width="640" height="480" allowfullscreen="true" webkitallowfullscreen="true" mozallowfullscreen="true"  frameborder="0"></iframe>
 
-## Why
+This project contains all design files for a **6:1 audio multiplexer** , meaning it can switch six analog inputs into one analog output. 
 
-Sometimes you just need more inputs. And this is how you do it.
+It is based on the [BD3491](https://www.digikey.de/product-detail/de/rohm-semiconductor/BD3491FS-E2/BD3491FS-E2TR-ND/5720882) which does everthing related to the Audio signals.
 
-## How
+On top of switching the inputs, it is also able to condition the signal. It can 
 
-The BD3491 does all the audio switching. It combines one 6 input switch and an equalizer into a simple package. 
-The STM32 configures the BD3491 to switch to the specified inputs based on pressed buttons or software control.
+- Apply Bass-Boosting and Treble-Boosting (essentially a crappy 3-Point Equalizer)
+- Amplify the input signal by up to 20dB
+- Add attenuation to the individual channels (aka. balance the left and right channel)
 
-# serial control Syntax
-Upon connecting the stm32 to a PC using USB it will register itself as a new Serial Port. The following text commands can be issued via said Serial connection (the baudrate is irrelevant): 
+All of these feature of the chip can be activated with the on-board STM32, which can in turn be controlled 
+with either on-board buttons or via it's integrated USB port. One can either use the serial protocol directly 
+or a [GUI written in python](gui/README.md)  
 
-- `C[number]\n` will change the input to the specified channel. The stm32 echo the command as it was understood. e.g: When Sending `C0\n` it will respond `C0\r\n` to acknowledge the channel switched to **Input 1**. When issuing a `C10` there will be no response, since 10 is out of range. *NOTE:* when using the buttons on the PCB to switch the input, the stm will also issue a `C[number]\r\n` over the serial port if it is connected to notify the PCB of the external input change. 
+The Board can be supplied over said USB port as well (if the primary use-case implies it beeing connected
+to the PC constantly) or by applying power using a 2.1mm Barrel Jack.
 
-- `G[number]\n` will activate an input gain of [number] in dB. It will also respond with the closest gain it can do. e.g: `G10` will result in the stm responding `G12\r\n` which means it will add a 12db input boost, which was the closest matching _valid_ input gain value. You can check the datasheet of the BD3491 to find the possible gain values if this peaks your interest :) 
+For more details on the pcb, check the [PCB readme](kicad/README.md)
 
-- `L[number]\n` or `R[number]\n` will activate an attenuator in either the left or the right channel. [number] is once again in dB. It works much like the `G`-command. Setting [number] to 0 will deactivate the Attenuation.
+For details on the Serial command syntax and firmware flashing instructions, check the [firmware readme](firmware/README.md)
 
-- `B[number]\n` or `T[number]\n` adds **B**ass or **T**reble gain to the output
 
-- `M[0/1]\n` will either mute or unmute the output
+# Why
+
+Because ? 
+
+Sometimes you just need more inputs. This is how you do it. 
 
-- `S[0/1]\n` will connect all inputs to the output 

firmware/Include/bd3491.h

@@ -20,9 +20,9 @@ int bd_set_gain(I2C_HandleTypeDef * handle, uint8_t gain_in_db);
 uint8_t bd_set_attenuation(I2C_HandleTypeDef * handle, uint8_t right_channel, uint8_t attenuation_in_db);
 
 // when gain == 0, cut bass boost
-void bd_set_bass_boost(I2C_HandleTypeDef * handle, uint8_t gain);
+uint8_t bd_set_bass_boost(I2C_HandleTypeDef * handle, uint8_t gain);
 // when gain == 0, cut treble boost
-void bd_set_treble_boost(I2C_HandleTypeDef * handle, uint8_t gain);
+uint8_t bd_set_treble_boost(I2C_HandleTypeDef * handle, uint8_t gain);
 
 enum BD_SOURROUND_GAIN {
 	BD_SOURROUND_OFF = 0,

firmware/Include/main.h

@@ -37,7 +37,20 @@ extern "C" {
 
 /* Exported types ------------------------------------------------------------*/
 /* USER CODE BEGIN ET */
+struct ui_state {
+  uint8_t oldchannel;
+  enum {
+    UI_STATE_NORMAL = 0, 
+    UI_STATE_MUTE,
+    UI_STATE_SHORT,
+  } state;
 
+  uint8_t gain;
+  uint8_t bboost, tboost;
+  uint8_t latt, ratt;
+};
+
+extern struct ui_state ui_state; // global ui state
 /* USER CODE END ET */
 
 /* Exported constants --------------------------------------------------------*/
@@ -54,8 +67,12 @@ extern "C" {
 void Error_Handler(void);
 
 void set_input(uint8_t channel);
+int get_input();
 void set_attenuation(uint8_t left, uint8_t right);
-void set_mute(uint8_t mute);
+void set_mute(uint8_t mute); //< tries to switch to muted ui state
+int is_muted(); //< returns whether the ui is muted
+void set_short(uint8_t shorted); //< tries to switch to shorted ui state
+int is_shorted();
 
 /* USER CODE BEGIN EFP */
 

firmware/README.md

@@ -0,0 +1,35 @@
+
+# Building the Firmware
+
+In order to build the firmware, [platformio](https://platformio.org/install/cli) must be installed. 
+
+To build the firmware, navigate to this folder using the terminal of your choice and type
+
+```bash
+platformio run
+```
+
+## Flashing the firmware 
+
+If you happen to have an stlink compatible interface (e.g the [programmer attached the nucleo-boards](https://jeelabs.org/book/1547a/])), 
+then (after connecting said interface to the PC and the PCB), 
+the firmware can be flashed with 
+
+```bash
+platformio run -t upload
+```
+
+# serial control Syntax
+Upon connecting the stm32 to a PC using USB it will register itself as a new Serial Port. The following text commands can be issued via said Serial connection (the baudrate is irrelevant): 
+
+- `C[number]\n` will change the input to the specified channel. The stm32 echo the command as it was understood. e.g: When Sending `C0\n` it will respond `C0\r\n` to acknowledge the channel switched to **Input 1**. When issuing a `C10` there will be no response, since 10 is out of range. *NOTE:* when using the buttons on the PCB to switch the input, the stm will also issue a `C[number]\r\n` over the serial port if it is connected to notify the PCB of the external input change. 
+
+- `G[number]\n` will activate an input gain of [number] in dB. It will also respond with the closest gain it can do. e.g: `G10` will result in the stm responding `G12\r\n` which means it will add a 12db input boost, which was the closest matching _valid_ input gain value. You can check the datasheet of the BD3491 to find the possible gain values if this peaks your interest :) 
+
+- `L[number]\n` or `R[number]\n` will activate an attenuator in either the left or the right channel. [number] is once again in dB. It works much like the `G`-command. Setting [number] to 0 will deactivate the Attenuation.
+
+- `B[number]\n` or `T[number]\n` adds **B**ass or **T**reble gain to the output
+
+- `M[0/1]\n` will either mute or unmute the output
+
+- `S[0/1]\n` will connect all inputs to the output 

firmware/Src/bd3491.c

@@ -64,19 +64,30 @@ int bd_set_gain(I2C_HandleTypeDef * handle, uint8_t gain_in_db) {
 uint8_t bd_set_attenuation(I2C_HandleTypeDef * handle, uint8_t right_channel, uint8_t attenuation_in_db) {
 	if ((attenuation_in_db&0x7F) > 87)
 		attenuation_in_db = BD_INF_ATTENUATION;
-
-	bd_write_reg(handle, 0x21 + right_channel, attenuation_in_db | 0x80);
+	
+	if (right_channel) 
+		right_channel = 1;
+	
+	bd_write_reg(handle, 0x22 - right_channel, attenuation_in_db | 0x80);
 	return attenuation_in_db;
 }
 
 // when gain == 0, cut bass boost
-void bd_set_bass_boost(I2C_HandleTypeDef * handle, uint8_t gain) {
+uint8_t bd_set_bass_boost(I2C_HandleTypeDef * handle, uint8_t gain) {
+	if (gain > 0x07) gain = 0x07;
+
 	bd_write_reg(handle, 0x51, (gain == 0)?(0x80):(0x00) | (gain&0x07) << 1);
+
+	return gain;
 }
 
 // when gain == 0, cut treble boost
-void bd_set_treble_boost(I2C_HandleTypeDef * handle, uint8_t gain) {
+uint8_t bd_set_treble_boost(I2C_HandleTypeDef * handle, uint8_t gain) {
+	if (gain > 0x07) gain = 0x07;
+
 	bd_write_reg(handle, 0x57, (gain == 0)?(0x80):(0x00) | (gain&0x07) << 1);
+
+	return gain;
 }
 
 void bd_set_sourround(I2C_HandleTypeDef * handle, enum BD_SOURROUND_GAIN gain) {

firmware/Src/main.c

@@ -102,58 +102,92 @@ int test_button_pressed() {
 #undef TEST_BUTTON
 }
 
-struct ui_state {
-  uint8_t oldchannel;
-  uint8_t mute;
-} ui_state = {
+struct ui_state ui_state = {
   .oldchannel = -1,
-  .mute = 0,
+  .state = UI_STATE_NORMAL,
 };
 
 void set_input(uint8_t channel) {
-	if (ui_state.oldchannel == channel || channel >= 6)
+	if (ui_state.state != UI_STATE_NORMAL || ui_state.oldchannel == channel || channel >= 6)
 		return;
 
-	set_input_led(ui_state.oldchannel, 0);
+  set_input_led(ui_state.oldchannel, 0);	
+  
+  set_input_led(channel, 1);
 
-  // do not disturb the mute mode
-  if (!ui_state.mute)
-  {
-	  set_input_led(channel, 1);
-
-	  // invert bd inputs to match the numbers on the case
-    bd_set_input(&hi2c1, 5-channel);
-  }
+  // invert bd inputs to match the numbers on the case
+  bd_set_input(&hi2c1, 5-channel);
 
 	ui_state.oldchannel = channel;
 
 	printf("C%d\n", channel);
 }
 
+int get_input() {
+  return ui_state.oldchannel;
+}
+
+// only mute if the ui allows to 
 void set_mute(uint8_t mute) {
-  if(ui_state.mute == mute)
+  if(UI_STATE_MUTE == ui_state.state && mute)
+    // no state change required
     return;
 
-  if (0 == (ui_state.mute = mute)) {
+  // figure out the state transition  
+  if (UI_STATE_NORMAL == ui_state.state && mute) {
+    ui_state.state = UI_STATE_MUTE;
+    HAL_GPIO_WritePin(USER_LED_GPIO_Port, USER_LED_Pin, 1);
+    set_input_led(ui_state.oldchannel, 0);
+    bd_set_input(&hi2c1, BD_INPUT_MUTE);
+  } 
+  else if (UI_STATE_MUTE == ui_state.state && !mute) 
+  {
+    ui_state.state = UI_STATE_NORMAL;
     // hack to make reactivation of the last channel easier
     uint8_t old_input = ui_state.oldchannel;
     ui_state.oldchannel = -1;
 
     set_input(old_input);
-    HAL_GPIO_WritePin(USER_LED_GPIO_Port, USER_LED_Pin, 0);
-  }
-  else {
-    HAL_GPIO_WritePin(USER_LED_GPIO_Port, USER_LED_Pin, 1);
-    set_input_led(ui_state.oldchannel, 0);
-    bd_set_input(&hi2c1, BD_INPUT_MUTE);
+    HAL_GPIO_WritePin(USER_LED_GPIO_Port, USER_LED_Pin, 0); 
   }
+}
 
-  printf("M%d\n", ui_state.mute?1:0);
+int is_muted() {
+  return ui_state.state == UI_STATE_MUTE;
+}
+
+void set_short(uint8_t do_short) {
+  // test for possible state changes
+  if (UI_STATE_NORMAL == ui_state.state && do_short) 
+  {
+    ui_state.state = UI_STATE_SHORT;
+    bd_set_input(&hi2c1, BD_INPUT_ALL);
+
+    // visualize that all inputs are shorted
+    for (int i = 0; i < 6; ++i) 
+      set_input_led(i, 1);
+  } 
+  else if (UI_STATE_SHORT == ui_state.state && !do_short) 
+  {
+    ui_state.state = UI_STATE_NORMAL;
+    
+    for (int i = 0; i < 6; ++i) 
+      set_input_led(i, 0);
+
+    // reactivate currently selected input
+    uint8_t old_input = ui_state.oldchannel;
+    ui_state.oldchannel = -1;
+    set_input(old_input);
+  }
+}
+
+int is_shorted() {
+  return ui_state.state == UI_STATE_SHORT;
 }
 
 void set_attenuation(uint8_t left, uint8_t right) {
-	bd_set_attenuation(&hi2c1, 0, left);
-	bd_set_attenuation(&hi2c1, 1, right);
+	ui_state.latt = bd_set_attenuation(&hi2c1, 0, left);
+  ui_state.ratt = bd_set_attenuation(&hi2c1, 1, right);
 }
 
 
@@ -202,6 +236,7 @@ int main(void)
   set_attenuation(0,0);
   int count = 0;
   int button_timeout = 0;
+  
   /* USER CODE END 2 */
 
   /* Infinite loop */
@@ -226,7 +261,8 @@ int main(void)
 
       if (1000 < button_timeout) {
         // long press, toggle mute
-        set_mute(!ui_state.mute);
+        set_mute(!is_muted());
+        printf("M%d\n", is_muted());
         button_timeout = 0;
       }
 

firmware/Src/message_parser.c

@@ -138,16 +138,24 @@ int parse_buffer() {
 			uint16_t gain;
 			if (next_arg_unsigned(&gain)) break;
 
-			printf("G%d\n", bd_set_gain(&hi2c1, gain));
+			printf("G%d\n", (ui_state.gain = bd_set_gain(&hi2c1, gain)));
 		}
 		break;
 	case 'L':
 	case 'R':
 	{
 		uint16_t att;
-		if (next_arg_unsigned(&att)) break;
+		uint8_t dir = 0;
+		uint8_t * save = &ui_state.latt;
 
-		printf("%c%d\n", temp, bd_set_attenuation(&hi2c1, temp == 'R', att&0xFF));
+		if (next_arg_unsigned(&att)) break;
+		
+		if (temp == 'R') {
+			dir = 1;
+			save = &ui_state.ratt;
+		}
+
+		printf("%c%d\n", temp, (*save = bd_set_attenuation(&hi2c1, dir, att&0xFF)));
 	}
 		break;
 	case 'M':
@@ -156,11 +164,46 @@ int parse_buffer() {
 		if (next_arg_unsigned(&mute)) break;
 		
 		set_mute(mute);
+		printf("M%d\n", is_muted());
+	}
+		break;
+	case 'S':
+	{
+		uint16_t shorted;
+		if (next_arg_unsigned(&shorted)) break;
+		
+		set_short(shorted);
+		printf("S%d\n", is_shorted());
 	}
 		break;
 	case 'B':
-	case 'T':
+	{
+		uint16_t boost;
+		if (next_arg_unsigned(&boost)) break;
 
+		printf("B%d\n", (ui_state.bboost = bd_set_bass_boost(&hi2c1, boost)));
+	}
+		break;
+	case 'T':
+	{
+		uint16_t boost;
+		if (next_arg_unsigned(&boost)) break;
+
+		printf("T%d\n", (ui_state.tboost = bd_set_treble_boost(&hi2c1, boost)));
+	}
+		break;
+	case '?':
+	{
+		// return the system state
+		printf("M%d\n", is_muted());
+		printf("S%d\n", is_shorted());
+		printf("C%d\n", get_input());
+		printf("B%d\n", ui_state.bboost);
+		printf("T%d\n", ui_state.tboost);
+		printf("L%d\n", ui_state.latt);
+		printf("R%d\n", ui_state.ratt);
+	}
+		break;
 	default:
 		printf("E\n");
 	}

gui/.vscode/settings.json

@@ -0,0 +1,3 @@
+{
+    "python.pythonPath": "/usr/bin/python"
+}

gui/app.spec

@@ -0,0 +1,33 @@
+# -*- mode: python ; coding: utf-8 -*-
+
+block_cipher = None
+
+
+a = Analysis(['app.py'],
+             pathex=['/home/julian/git/audioMux/gui'],
+             binaries=[],
+             datas=[],
+             hiddenimports=[],
+             hookspath=[],
+             runtime_hooks=[],
+             excludes=[],
+             win_no_prefer_redirects=False,
+             win_private_assemblies=False,
+             cipher=block_cipher,
+             noarchive=False)
+pyz = PYZ(a.pure, a.zipped_data,
+             cipher=block_cipher)
+exe = EXE(pyz,
+          a.scripts,
+          a.binaries,
+          a.zipfiles,
+          a.datas,
+          [],
+          name='app',
+          debug=False,
+          bootloader_ignore_signals=False,
+          strip=False,
+          upx=True,
+          upx_exclude=[],
+          runtime_tmpdir=None,
+          console=False )

gui/icon.svg

@@ -0,0 +1,77 @@
+<?xml version="1.0" encoding="UTF-8" standalone="no"?>
+<!-- Created with Inkscape (http://www.inkscape.org/) -->
+
+<svg
+   xmlns:dc="http://purl.org/dc/elements/1.1/"
+   xmlns:cc="http://creativecommons.org/ns#"
+   xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
+   xmlns:svg="http://www.w3.org/2000/svg"
+   xmlns="http://www.w3.org/2000/svg"
+   xmlns:sodipodi="http://sodipodi.sourceforge.net/DTD/sodipodi-0.dtd"
+   xmlns:inkscape="http://www.inkscape.org/namespaces/inkscape"
+   width="10mm"
+   height="10mm"
+   viewBox="0 0 10 10"
+   version="1.1"
+   id="svg8"
+   inkscape:version="0.92.4 5da689c313, 2019-01-14"
+   sodipodi:docname="icon.svg"
+   inkscape:export-filename="/home/julian/git/audioMux/gui/icon/1.png"
+   inkscape:export-xdpi="325.12"
+   inkscape:export-ydpi="325.12">
+  <defs
+     id="defs2" />
+  <sodipodi:namedview
+     id="base"
+     pagecolor="#ffffff"
+     bordercolor="#666666"
+     borderopacity="1.0"
+     inkscape:pageopacity="0.0"
+     inkscape:pageshadow="2"
+     inkscape:zoom="5.6"
+     inkscape:cx="4.446261"
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+     inkscape:document-units="mm"
+     inkscape:current-layer="layer1"
+     showgrid="false"
+     inkscape:window-width="1918"
+     inkscape:window-height="1058"
+     inkscape:window-x="0"
+     inkscape:window-y="20"
+     inkscape:window-maximized="1" />
+  <metadata
+     id="metadata5">
+    <rdf:RDF>
+      <cc:Work
+         rdf:about="">
+        <dc:format>image/svg+xml</dc:format>
+        <dc:type
+           rdf:resource="http://purl.org/dc/dcmitype/StillImage" />
+        <dc:title />
+      </cc:Work>
+    </rdf:RDF>
+  </metadata>
+  <g
+     inkscape:label="Ebene 1"
+     inkscape:groupmode="layer"
+     id="layer1"
+     transform="translate(0,-287)">
+    <circle
+       style="color:#000000;overflow:visible;fill:none;fill-opacity:1;fill-rule:nonzero;stroke:#298f29;stroke-width:0.9441849;stroke-linecap:round;stroke-miterlimit:4;stroke-dasharray:none;stroke-opacity:1"
+       id="path815"
+       cx="5"
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+       r="4.5279074" />
+    <text
+       xml:space="preserve"
+       style="font-size:4.23333311px;line-height:125%;font-family:Sans;letter-spacing:0px;word-spacing:0px;fill:#000000;fill-opacity:1;stroke:#beb3b3;stroke-width:0.26458332px;stroke-linecap:butt;stroke-linejoin:miter;stroke-opacity:1;"
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+  </g>
+</svg>

gui/tray.py

@@ -0,0 +1,55 @@
+import wx
+from wx import adv
+
+def create_menu_item(menu, label, func):
+    item = wx.MenuItem(menu, -1, label)
+    menu.Bind(wx.EVT_MENU, func, id=item.GetId())
+    menu.AppendItem(item)
+    return item
+
+
+class Tray(wx.adv.TaskBarIcon):
+    def __init__(self, parent):
+        super().__init__()
+        self.Bind(wx.adv.EVT_TASKBAR_LEFT_DOWN, self.OnLeftDown)
+        self.SetIcon(wx.Icon("icon/1.png"))
+        self.parent = parent
+
+    def CreatePopupMenu(self):
+        menu = wx.Menu()
+        hidem = wx.MenuItem(menu, wx.ID_ANY, 'Show Window')
+        menu.Bind(wx.EVT_MENU, self.ShowParent, id=hidem.GetId())
+        menu.Append(hidem)
+        menu.AppendSeparator()
+        
+        quitm = wx.MenuItem(menu, wx.ID_ANY, 'Quit')
+        menu.Bind(wx.EVT_MENU, self.OnExit, id=quitm.GetId())
+        menu.Append(quitm)
+        return menu
+
+    def CreateSelectionMenu(self):
+        return None
+
+    def OnLeftDown(self, event):
+        menu = self.CreateSelectionMenu()
+        if menu:
+            self.PopupMenu(menu)
+        
+  
+    def OnExit(self, event):
+        # close self and parent
+        wx.CallAfter(self.Destroy)
+        wx.CallAfter(self.parent.Destroy)
+
+    def ShowParent(self, evt):
+        self.parent.Show()
+
+if __name__ == "__main__":
+    app = wx.App()
+
+    
+    # create an empty frame to keep the main loop running
+    Tray(wx.Frame(None))
+    
+    app.MainLoop()
+    

kicad/README.md

@@ -0,0 +1,29 @@
+![THE PCB](../doc/audioMux-brd.svg)
+
+There are a total of six solderjumpers on the board:
+
+# switching to the barrel jack as voltage supply
+
+*JP3* and *JP4* set the source for the supply voltage. 
+*JP4* connects the voltage input to the barrel jack, *JP4* connects it to the USB +5V rail.
+
+Per Default JP4 is closed and JP3 is open, making the default way of supplying voltage the USB jack. 
+
+If the Barrel Jack should be used, then **JP4 has to be opened first** by cutting the trace which shorts it by default, otherwise **the USB voltage will be shorted with the barrel jack, causing potential damage to the USB port**.
+Afterwards, *JP3* can be closed with a small blob of solder. 
+
+# activating the equalizer
+
+*JP1* and *JP2* connect the output of the Audio switching part of the Rohm chip. 
+When left in the default setting, they will connect them to the output jack directly, bypassing the Equalisation part of the chip completely.
+
+By selecting the other possible path, the equalisation circuit becomes usable. For this to work, 
+*JP7* and *JP8* have to be closed with small solder blobs as well, since those connect the equalizers 
+output to the output audio jack.
+
+# Assembling the rest 
+
+For assembly of the board, check the [documentation folder](../doc). It contains the [interactive bill of materials](../doc/interactive_placement.html),
+which indicates what components go where.
+
+Also take a look at the [BOM](../doc/BOM.xlsx) for what components can be sourced where.