Awesome PocketSDR (order of hardware parts)

category: gnss

Table of contents

Introduction

I am aiming to create PocketSDR that Professor Tomoji Takasu of Tokyo University of Marine Science and Technology published on GitHub.

It is a software defined radio (SDR) that receives GNSS (global navigation satellite system) radiowaves, and consists of radiowave reception hardware design materials and satellite signal processing software. In particular, this software not only allows us to look into the backyard of satellite positioning receivers, but also demodulates the latest signals that are not yet available on the market, so I am crazy about it.

PocketSDR has a collection of design materials so that many people can retest their hardware. A configuration file tuned for Maxim MAX2771, an IC that captures GNSS signals, is also included.

In this time, I placed an order for a printed circuit board (PCB) and parts based on this hardware design material. By nature, hardware creation is time-consuming. However, PocketSDR is awesome because the materials are prepared so that parts can be ordered with a small number of man-hours.

Ordering printed circuit boards and stencil

PocketSDR provides Autodesk EAGLE format files for printed circuit boards for wiring between components. An Autodesk account is required to use the printed circuit board CAD software EAGLE. I created an Autodesk academic account when I used the CAD software Autodesk Fusion 360 before, so I used it this time. I think you can also create this Gerber file with a free account for hobbyists (electronic work enthusiasts).

If you open the board file pocket_sdr_v2.1.brd in the PocketSDR HW (hardware) directory with EAGLE, the printed circuit board screen will be displayed.

PocketSDR PCB design on EAGLE

EAGLE has a configuration file for creating an order file for Fusion PCB of Seeed Studio, so I used it. Of course, you can also create a Gerber file for ordering other than Fusion PCB.

Seeed FusionPCB - How to output Gerber files from Autodesk Eagle

I uploaded the Gerber file pocket_sdr_v2.1.zip created in this way to the Fusion PCB.

FusionPCB

When I uploaded the Gerber file, the printed circuit board size was updated to that of this file. The standard number of printed circuit boards is 10. We could change this to 5, but the creation fee did not change.

Next, I uploaded the Gerber file for creating the stencil (metal mask). The stencil is used to cover the printed circuit board and apply the solder cream from above.

It seems to upload the one on the solder side as a Gerber file for the stencil.

We can choose from two types of stencil size, but this time the smaller one is enough. The price is also a little cheaper.

FusionPCB

The total price of the printed circuit board and stencil was 13.8 USD. I paid about 4,000 JPY via PayPal including shipping fee. The shipping fee is high.

DESCRIPTION            UNIT PRICE   QTY   AMOUNT       
PCB Stencil Service    $8.90 USD    1     $8.90 USD    
Item# 503000001                                        
Fusion PCB             $4.90 USD    1     $4.90 USD    
Item# 501010001                                        
Discount/ShippingFee   $17.27 USD   1     $17.27 USD   
Subtotal                                  $31.07 USD   
Total                                     $31.07 USD

Ordering parts

To order parts, use the Excel file pocket_sdr_v2.1_parts.xlsx in the HW (hardware) directory of PocketSDR. This file contains your Digi-Key part number, so you can simply upload it to Digi-Key web site and the part name and quantity will be entered automatically.

PocketSDR Digi-Key

If the total amount is 6,000 yen or more in the Japan Digi-Key, the shipping fee will be exempted. Here, the assembly column is set to 2 so that 2 sets can be created. Unfortunately, some items including the key part MAX2771 is out of the stock. In addition, since printed circuit boards and screws are also described in this parts list, parts other than those ordered from Digi-Key are also excluded from the list.

PocketSDR Digi-Key confirmation

“Order carried forward” is written in the column of memory chip AT24C128C. This seems to mean that we are currently out of stock for the quantity and will be shipped as soon as it is available. First of all, I also removed this carry-forward order from the parts list because I want to get parts in stock.

Digi-Key export control

Next, we will be asked for export control information along with your delivery address. I use PocketSDR for myself, so I chose No for resale and consumer for the application. As additional information, I’d really like to write “super, special, ultra-high performance GNSS receiver”, but here I safely chose “GPS receiver”.

Digi-Key delivery

We can choose the shipping method from either “UPS Worldwide Saver” or “FedEx International Priority”. Somehow, Saver has an inexpensive image, and Priority has a high-class image. Here, the shipping fee is exempted and the delivery days are the same, so I chose UPS so as not to put an unnecessary burden. If we purchase goods from overseas, we may be charged an import tax and a handling fee when we forget. I am grateful that the price here includes tariffs.

Digi-Key payment

Set the payment method, review the entire order, press the order button and the order is complete. I paid for it with PayPal.

This time, due to out of stock, the following items could not be ordered.

2 Receiver IC Maxim MAX2771ETI+
1 EEPROM Microchip AT24C128C-XHM-T
1 Bias-T Mini-Circuits TCBT-2R5G+
1 TCXO Epson TG2520SMN 24.0000M-MCGNNM3

I’m going to look for these parts.

Afterwards

(2022-05-04)
I placed an order Mini-Circuits Bias-T TCBT-2R5G+ with Mini-Circuits Yokohama, a distributor of Mini-Circuits in Japan. The minimum ordering unit seems to be 10, and it was 13,500 yen including shipping and handling.

TCBT-2R5G+

I also placed an order Epson’s TCXO TG2520SMN 24.0000M-MCGNNM3 with Core Staff Online. I ordered 4 pieces including the spare and it was 3,607 yen including the shipping fee.

The remaining unordered parts are Maxim MAX2771ETI+ and Microchip AT24C128C-XHM-T.

I received the printed circuit board and stencil. It’s much smaller than the size of a palm and it’s amazing.

PocketSDR PCB

(2022-05-07)
At Digi-Key, Maxim MAX2771ETI+ (GNSS signal reception IC) and Microchip AT24C128C-XHM-T (EEPROM) could be ordered, so I ordered them a little more including spares. The delivery date for MAX2771 is undecided, and the delivery date for AT24C128C is September. I’m looking forward to it. This completes the order for all parts.

Digi-Key

Conclusion

The parts for PocketSDR hardware could be ordered with a small number of man-hours. Arrangement of remaining parts, fun production, and fun experiments are waiting for me.