Wei: FM

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2020年6月22日星期一

FM Transceivers (en)

Why this

With these strategies, it is now much easier to develop device drivers. Therefore, I wrote Python drivers for several FM transceiver modules (Si4713, RDA5820N, KT0803L). Repository is here.

Transceiver modules

A transmitter which can also measure noise(signal) level of a particular frequency.
Can send RDS message.
Popular, resource (documents and sample code are well available).

Transmitter mode only.
Noisy.
Cheap and well available.

Can switch between transmitter / receiver / audio-amplifier / ADC modes.
Can send RDS message.
PLL locks very slowly.
Rare, documents and resources are rare.
Website is not reachable.

How to use

Usage and test methods are here and here。
USB-I2C converter is required if you want to control transceivers with PC, options are:

Using FT232H with Bridges package as USB-I2C converter。
Using FX2LP with this firmware, cheaper and faster. Also, FX2LP package is required.

There are xxxxx_proxy.py modules with smaller size to be used on ESP32.

Test Results

Si4713

Basic functional test

with FX2LP USB-I2C converter and Jupyter notebook

Basic functional test

with ESP32 and MicroPython Remote Kernel + Jupyter notebook

RDS transmission test

RDA5820N

Basic functional test

KT0803L

to be added

Dependencies:

FM Transceivers

緣由
採用這套策略之後，開發 device driver 變得容易且快速多了，於是為手上的幾個 FM transceiver 模組 (Si4713, RDA5820N, KT0803L) 也寫了 Python drivers，放在這裡。

模組特性

主要是 transmitter 的功能。
也可以量測指定頻率的訊號強度。
可以發送 RDS 訊息。
市面上較常見，開發資源較多。

只有 transmitter 的功能。
Noise floor 會整個被抬高，很吵。
市面上常見，較便宜。

具有 transmitter / receiver / audio-amplifier / ADC 的功能，可以任選一種模式切換。
可以發送 RDS 訊息。
切換頻率的時候 PLL lock 的速度很慢。
使面上較少見，開發資源較少。
官網連不上。

使用方式

所有的測試與使用方式，都記錄在這裡和這裡。
需搭配 USB-I2C converter，例子:

使用 FT232H 搭配 Bridges package 來作為 USB-I2C converter。
使用 FX2LP 搭配這個韌體來做為 USB-I2C converter，速度更快。另需要搭配 FX2LP。

如果要上傳到 ESP32 上面使用，可以用體積較小的 xxxxx_proxy.py 。

測試結果

Si4713

Basic functional test

with FX2LP USB-I2C converter and Jupyter notebook

Basic functional test

with ESP32 and MicroPython Remote Kernel + Jupyter notebook

RDS transmission test

RDA5820N

Basic functional test

KT0803L

to be added

Dependencies:

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