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-# Voltage Reference Generator
+# AD5791/AD5781 Voltage Reference Generator
+
+![MainPicture](docs/main-picture.jpeg)
+
+## Introduction
+
+This full open source precision voltage reference generator consists of LM399 as reference and AD5781/5791 DAC.
+
+Resistors used to convert LM399 voltage to 10V is ten 0805 resistors with specification of 20ppm/C. The tested temperature coefficient is around 5ppm/C under 0~60 degree C. The whole device is around 3ppm/C.
+
+## Highlights
+
+- Cheap. Both AD5781 and LM399 can be reached with pretty low prices, and 20ppm/C resistors are super cheap.
+- Full open source. This repo consists of all the sources(links) include hardware to replicate.
+- Portable. Palm-sized device with 220V as main supply.
+
 ## Hardware
-LM399
-Statistic method for ref boost up.
-AD5791 - the 2-bit 1ppm INL DAC
-STM32F030 as the controller
-USB isolated UART input
+
+Main reference: LM399 with statistic resistors booted up to 10V
+
+DAC: AD5791/AD5781
+
+ADT7420: internal temperature monitor(can be omitted)
+
+Display: 10 digits segments LED display
+
+MainController: STM32F030
+
+USB to isolated UART for remote control
+
+Encoder for manual control
+
+## Gallery
+
+![inside-overview](docs/inside-overview.png)
+
+![lm399-and-ad5791](docs/lm399-and-ad5791.png)
+
+![front-panel](docs/front-panel.png)
+
+![back-panel](docs/back-panel.png)
+
+![enclosure-back](docs/enclosure-back.png)
+
+![power-and-usb](docs/power-and-usb.png)
+
+
+
 ## Test Result
-TBD
+
+1. INL
+
+2. Temp-drift
+
+3. TBD
+
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