Board-dat/DPR/DPR1098-dat/DPR1098-dat.md
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@@ -8,12 +8,18 @@
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### Board Map, Dimension, Pins, chip info, etc.
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-
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+- [[DPR1097-dat]]
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## Applications, category, tags, etc.
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+
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+
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## Demo Code and Video
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+
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+
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+
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+
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## ref
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- [[DPR1098]] - [[DPR1097-dat]]
Chip-dat/Maxim-dat/2025-11-23-18-27-33.png
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Binary files /dev/null and b/Chip-dat/Maxim-dat/2025-11-23-18-27-33.png differ
Chip-dat/Maxim-dat/MAX3490-dat.md
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@@ -22,4 +22,12 @@ If your system uses a **3.3V power supply**, the **MAX3490** is the appropriate
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For 3.3V systems, use the **MAX3490**:
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- Fully compatible with 3.3V logic levels
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- Drop-in solution for RS-485/RS-422 communication
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-- Low-power and ESD-protected
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\ No newline at end of file
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+- Low-power and ESD-protected
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+
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+![](2025-11-23-18-27-33.png)
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+
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+
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+## ref
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+
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+- [[MAX490-dat]] - [[maxim-dat]] - [[analog-device-dat]]
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+
Chip-dat/Maxim-dat/MAX490-dat/MAX490-dat.md
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@@ -10,3 +10,4 @@
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## Receiver Input Voltage Range
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- **Common-mode voltage range:** -7V to +12V
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+- [[RS422-dat]]
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Circuits-dat/circuits-dat.md
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@@ -14,6 +14,8 @@
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- [[mosfet-dat]] - [[logic-gate-dat]]
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+- [[open-drain-open-collector-dat]] - [[push-pull-driver]]
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+
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- [[auto-serial-dat]]
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Circuits-dat/open-drain-open-collector-dat.md
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+
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+# open-drain-open-collector-dat
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+
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+# Open-Drain vs Open-Collector
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+
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+Both are output types that **can pull LOW but cannot drive HIGH**.
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+A pull-up resistor is required to generate the HIGH level.
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+
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+---
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+
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+# 1️⃣ Open-Collector (OC)
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+
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+- Uses an **NPN bipolar transistor**
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+- Can **pull output LOW**
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+- Cannot **drive output HIGH** → needs external pull-up resistor
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+
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+## How it works
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+- Transistor ON → output pulled to GND → **LOW**
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+- Transistor OFF → output floats → pull-up resistor → **HIGH**
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+
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+## Common uses
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+- I²C
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+- Interrupt lines
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+- Wired-OR / wired-AND logic
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+- Level shifting (pull-up to different voltage)
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+
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+---
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+
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+# 2️⃣ Open-Drain (OD)
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+
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+- Same behavior as open-collector
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+- Uses an **NMOS FET** instead of an NPN transistor
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+
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+## How it works
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+- FET ON → output pulled LOW
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+- FET OFF → pull-up resistor → HIGH
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+
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+## Common uses
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+- Modern low-voltage ICs
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+- I²C bus
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+- Shared interrupt lines
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+
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+---
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+
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+# 3️⃣ Why use open-drain / open-collector?
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+
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+Because multiple devices can safely share one wire:
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+
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+- Any device can pull the line LOW
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+- No device ever drives HIGH → **no short-circuit conflict**
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+
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+This enables **wired-AND / wired-OR logic**.
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+
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+---
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+
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+# 4️⃣ Comparison Table
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+
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+| Feature | Open-Collector | Open-Drain |
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+|--------|----------------|------------|
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+| Device type | NPN transistor | NMOS FET |
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+| Pulls LOW? | ✔️ Yes | ✔️ Yes |
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+| Drives HIGH? | ❌ No | ❌ No |
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+| Needs pull-up resistor? | ✔️ Yes | ✔️ Yes |
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+| Common in | Older TTL/CMOS | Modern ICs |
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+| Functional behavior | Same | Same |
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+
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+---
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+
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+# 5️⃣ Key Point
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+
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+**Open-drain and open-collector behave the same.**
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+The name only depends on the type of transistor used.
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+
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+## ref
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+
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+- [[circuits-dat]]
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\ No newline at end of file
Circuits-dat/push-pull-driver-dat.md
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+
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+# push-pull-driver-dat.md
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+
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+```markdown
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+# Push-Pull Driver (Totem-Pole Output)
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+
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+A **push-pull driver** is an output stage that uses **two active transistors**:
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+
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+- One transistor **pushes** the output HIGH
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+- Another transistor **pulls** the output LOW
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+
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+The output is actively driven in **both directions**.
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+
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+---
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+
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+# How Push-Pull Works
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+
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+- **HIGH output:**
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+ The upper transistor turns ON → output driven to Vcc
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+- **LOW output:**
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+ The lower transistor turns ON → output driven to GND
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+- Never both ON at the same time (to avoid shoot-through)
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+
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+This is also called a **totem-pole output**.
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+
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+---
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+
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+# Characteristics
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+
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+| Feature | Push-Pull Driver |
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+|--------|-------------------|
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+| Drives HIGH? | ✔️ Yes (actively) |
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+| Drives LOW? | ✔️ Yes (actively) |
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+| Needs pull-up resistor? | ❌ No |
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+| Speed | Very fast edges |
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+| Output impedance | Low |
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+| Can multiple outputs connect together? | ❌ No (will short-circuit) |
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+
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+---
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+
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+# Advantages
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+
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+- Fast transitions
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+- Strong driving capability
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+- No external pull-up needed
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+- Precise logic levels
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+
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+---
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+
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+# Disadvantages
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+
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+- **Cannot be wired together** with another push-pull output
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+- If two devices drive the same line at different levels → **short circuit**
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+
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+A **push-pull driver** is an output that actively drives both HIGH and LOW, unlike open-drain/open-collector which only pull LOW and rely on a pull-up resistor for HIGH.
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+
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+
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+## ref
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+
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+- [[circuits-dat]]
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\ No newline at end of file
Tech-dat/Interface-dat/RS422-dat/RS422-dat.md
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@@ -37,6 +37,67 @@ this probably wrong or not P2P type
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+## push pull resistor for fail-safe biasing
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+
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+**Only needed** if the bus can become *idle* (tri-state) and needs *fail-safe biasing*.
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+
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+---
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+
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+# 1. Point-to-Point RS-422
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+**No pull-ups needed.**
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+
49
+- MAX490 outputs are **push-pull** (active drivers)
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+- They actively drive both HIGH and LOW
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+- A/B will not float
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+
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+---
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+
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+# 2. RS-485-Style Multi-Drop Bus (Tri-state Idle)
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+If your system has:
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+
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+- multiple receivers
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+- drivers that may **disable** (tri-state)
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+- moments where *no one is driving the line*
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+
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+→ Then you **must add bias resistors**.
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+
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+### Typical fail-safe bias network:
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+- **A → Pull-up 680–1kΩ**
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+- **B → Pull-down 680–1kΩ**
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+- **120Ω termination across A–B**
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+
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+This ensures the bus stays in a known “mark” state.
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+
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+---
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+
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+# 3. Driver Always Enabled
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+**No bias resistors required.**
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+
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+MAX490 will drive the line at all times → never floating.
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+
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+---
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+
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+# 4. Receiver Inputs Only
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+**Usually no pull-ups needed.**
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+
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+- MAX490 receiver includes **internal fail-safe**
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+- Output goes HIGH if inputs:
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+ - are open,
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+ - shorted,
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+ - or idle.
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+
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+---
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+
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+# Summary Table
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+
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+| Scenario | Need Pull-up/Down? | Reason |
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+|---------|---------------------|--------|
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+| Point-to-point RS-422 | ❌ No | Push-pull driver |
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+| Multi-drop RS-485-like bus | ✔️ Yes | Bus can float when idle |
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+| Driver always enabled | ❌ No | Never tri-states |
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+| Receiver-only use | ❌ No | Internal fail-safe exists |
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+
100
+
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## ref
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42 103
https://en.wikipedia.org/wiki/RS-422
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@@ -46,5 +107,6 @@ https://www.omega.com/en-us/resources/rs422-rs485-rs232
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- [[RS422]] - [[DPR1097]]
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110
+- [[push-pull-driver]] - [[open-drain-open-collector-dat]] - [[circuits-dat]]
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50 112