checkpoint

config/sitemap.json

@@ -9721,6 +9721,10 @@
         "reference/device-os/libraries/n/NFC_UICR_RK.md": {
             "hash": "36a001fb0db71f23921ab242277114b287234eb8d1f7a0387fd91f6a8890e6c8",
             "date": "2025-05-01"
+        },
+        "hardware/community/input-protection.md": {
+            "hash": "40af93904cce7e7bc72b6fd9cea81e870f6c50a015cf0949912b1c188d6dd987",
+            "date": "2025-05-05"
         }
     }
 }

generated/api-service.json

@@ -13080,6 +13080,12 @@
             "group": "Success 200",
             "type": "String",
             "optional": false,
+            "parentNode": {
+              "path": "product",
+              "field": "product",
+              "type": "Object",
+              "isArray": false
+            },
             "field": "product.id",
             "isArray": false,
             "description": "<p>Product Unique ID</p>"
@@ -13088,6 +13094,12 @@
             "group": "Success 200",
             "type": "Number",
             "optional": false,
+            "parentNode": {
+              "path": "product",
+              "field": "product",
+              "type": "Object",
+              "isArray": false
+            },
             "field": "product.product_id",
             "isArray": false,
             "description": "<p>Product Firmware ID</p>"
@@ -13096,6 +13108,12 @@
             "group": "Success 200",
             "type": "String",
             "optional": false,
+            "parentNode": {
+              "path": "product",
+              "field": "product",
+              "type": "Object",
+              "isArray": false
+            },
             "field": "product.name",
             "isArray": false,
             "description": "<p>Product Name</p>"
@@ -13104,6 +13122,12 @@
             "group": "Success 200",
             "type": "String",
             "optional": false,
+            "parentNode": {
+              "path": "product",
+              "field": "product",
+              "type": "Object",
+              "isArray": false
+            },
             "field": "product.slug",
             "isArray": false,
             "description": "<p>URL compatible version of name</p>"
@@ -13112,6 +13136,12 @@
             "group": "Success 200",
             "type": "String",
             "optional": false,
+            "parentNode": {
+              "path": "product",
+              "field": "product",
+              "type": "Object",
+              "isArray": false
+            },
             "field": "product.description",
             "isArray": false,
             "description": ""
@@ -13120,6 +13150,12 @@
             "group": "Success 200",
             "type": "Number",
             "optional": false,
+            "parentNode": {
+              "path": "product",
+              "field": "product",
+              "type": "Object",
+              "isArray": false
+            },
             "field": "product.platform_id",
             "isArray": false,
             "description": "<p>Product Platform ID</p>"
@@ -13128,6 +13164,12 @@
             "group": "Success 200",
             "type": "String",
             "optional": false,
+            "parentNode": {
+              "path": "product",
+              "field": "product",
+              "type": "Object",
+              "isArray": false
+            },
             "field": "product.organization",
             "isArray": false,
             "description": "<p>Organization Unique ID</p>"
@@ -13136,6 +13178,12 @@
             "group": "Success 200",
             "type": "Boolean",
             "optional": false,
+            "parentNode": {
+              "path": "product",
+              "field": "product",
+              "type": "Object",
+              "isArray": false
+            },
             "field": "product.requires_activation_codes",
             "isArray": false,
             "description": ""
@@ -13144,6 +13192,12 @@
             "group": "Success 200",
             "type": "String",
             "optional": false,
+            "parentNode": {
+              "path": "product",
+              "field": "product",
+              "type": "Object",
+              "isArray": false
+            },
             "field": "product.device_protection",
             "isArray": false,
             "description": "<p>The set device protection status of the devices in this product</p>"

src/content/hardware/community/input-protection.md

@@ -0,0 +1,83 @@
+---
+title: Input protection
+columns: two
+layout: commonTwo.hbs
+description: Input protection
+---
+
+# {{title}}
+
+Most Particle devices have a 3.3V limit on digital and analog inputs. When connecting to external sensors, it's important to make sure:
+
+- The voltage is in the required range
+- The Particle device is protected against transient voltages
+
+One common solution is to use a rail-to-rail TVS (transient voltage suppressor) with Zener diode.
+
+The examples here use a Diodes Inc. [D1213A-02SOL-7](https://www.digikey.com/en/products/detail/diodes-incorporated/D1213A-02SOL-7/3340437) 
+(TVS DIODE 3.3VWM 10VC SOT233). They're US$ 0.20 in single quantities and significantly less expensive in larger quantities. This version is in the SOT-23-3 package 
+but there are variations in several common surface mount packages.
+
+This chip isn't available in PTH packages for breadboards, but if you want to prototype a design in a breadboard, you can 
+easily search for "SOT-23-3 breakout" and find items such as this one [from Amazon](https://www.amazon.com/Chironal-Double-Side-SOT23-3-Adapter-Converter/dp/B07MQBF2DD/ref=sr_1_3) which is 50 pieces for US$ 9.49. The SOT-23-3 is intended to be reflow soldered, but the pins are far enough apart that you can
+solder it by hand with a soldering iron fairly easily.
+
+## Example circuits
+
+### Voltage divider (5V)
+
+One common situation is interfacing a 5V signal to 3.3V GPIO. A common solution, especially for analog signals, is a voltage divider:
+
+![5V divider](/assets/images/hardware-community/input-protection/div5.png)
+
+These resistors values do not exactly match 5 VDC to 3.3V (4095 on the ADC), but are close and use common off-the-shelf resistor values.
+
+Because resistors in series add together, you could make this will three common 10K resistors, as well.
+
+![5V divider](/assets/images/hardware-community/input-protection/div5b.png)
+
+
+### Voltage divider (12V)
+
+This is a voltage divider for a 12 VDC signal, 27K on the high side, and 10K on the low side.
+
+![12V voltage divider](/assets/images/hardware-community/input-protection/div12.png)
+
+These resistors values do not exactly match 12 VDC to 3.3V (4095 on the ADC), but are close and use common off-the-shelf resistor values.
+
+### 3.3V TVS
+
+In the simplest case, a 3.3V analog or digital signal, you can use it like this:
+
+![IN4](/assets/images/hardware-community/input-protection/in4.png)
+
+- The input signal is `IN4` in this example.
+- It connects to `A0` though and analog or digital input can be used.
+- The 100Ω resistor protects against excessive current through the diode.
+- If the input voltage is negative, the diode shunts it to ground, protecting the MCU.
+- If the input signal is slightly more than 3.3V, the diode shunts it to 3V3, protecting the MCU.
+- If the input signal is very large, including ESD, the Zener diode stops the highest voltages, leaving the small differential to the rail-to-rail diodes.
+
+### 5V TVS
+
+You can also attach a voltage divider to the input of the TVS:
+
+![IN4](/assets/images/hardware-community/input-protection/div5tvs.png)
+
+- The voltage divider works the same as [Voltage divider (5V)](#voltage-divider-5v-), above.
+- Instead of the 100Ω R20 in [3.3V TVS](#3-3v-tvs), above, the high side of the voltage divider (R19) limits the input current.
+
+### Input block
+
+One technique that I like is to use this universal input block on my circuits. If I might want to change the voltage or other characteristics
+of the input in the future, I can just rework the board to change the resistors and not have to spin a new board.
+
+#### 3.3V Input block
+
+This circuit is electrically the same as [3.3V TVS](#3-3v-tvs).
+
+![IN1](/assets/images/hardware-community/input-protection/in1.png)
+
+The layout on a circuit board looks like this:
+
+![IN1](/assets/images/hardware-community/input-protection/in1-board.png)

src/content/hardware/newMenu.json

@@ -414,6 +414,10 @@
                 {
                     "dir": "monitor-one-modbus",
                     "title": "Monitor One getting started with Modbus"
+                },
+                {
+                    "dir": "input-protection",
+                    "title": "Input protection"
                 }
             ]
         }