What should we do a Chinese router?

    Good day, dear Habrazhiteli!

    Since my last publication, a lot of time has passed and enough projects have already been completed. As usual after publication, we received a lot of proposals for the development of varying degrees of severity. This includes watch watches for children, car trackers based on the Raspberry Pi, unknown devices with the condition of preliminary signing of the NDA, and other gadgets. Unfortunately, for a number of reasons, the proportion of launched projects is very low, I hasten to tell the story of one of them in hot pursuit.

    Once a non-core proposal was received for the purchase and delivery from China of a batch of mini-routers with the function of organizing a WiFi-Ethernet bridge. Those who are interested in what came of it, please welcome under the cat.

    So, there is a request for the supply of a batch of routers with a size of 1000 - we proceed to the search.

    For orders in everyday work, we use the well-known resource www.taobao.com if you need to purchase something ready-made or www.1688.com (Chinese version of www.alibaba.com ) if you need to purchase samples, a batch from the manufacturer or order services.

    A quick review gave 2 main applicants for the supply: Vonets VAR11N (price from 60rmb / pcs from 500 pieces) and the well-known TP-LINK TL-WR802N (price from 61rmb / pc from 500 pieces). The basic requirements are consistent, the price is reasonable - we purchase samples for testing. Upon receipt, we disassemble, analyze for compliance with customer requirements and send for approval.

    The customer liked the router samples, but when developing the final design, innovations were formulated. It is required to use + 12V power supply, change the dimensions of the printed circuit board, and also realize the possibility of direct soldering of twisted pair cable to the board in order to save space.

    The preliminary assessment that increasing the board area and adding DC-DC + 12V -> + 5V is not a difficult task was soon confirmed. One of the positions in the catalog of the manufacturer of routers colorfully reported on the possibility of modifying routers for acceptable ones from 45rmb / unit with a batch of 500 units.

    We formulate the terms of reference and request possible conditions from the manufacturer. In preliminary correspondence, the project was solved easily and simply, but in any case it is necessary to visit the factory. Therefore, we equip the delegation, accompanied by an ethnic Chinese translator, and move forward, it’s good to get a taxi for 20 minutes. Here, an event occurred that changed the entire course of the project.

    In the process of discussing technical and financial details, the manufacturer informed us that the service for the production of custom routers is much more expensive. “It turns out” that they have old prices on their site that they “just forgot to update,” so now a custom router will cost from 65rmb / unit for a batch of 500 units. Before we left the factory, we updated the information on the site.

    Yes, it happens of course - we look further. Further searches on the Chinese Internet showed many different devices suitable for parameters from 36rmb / pc, but the precipitate was already left and could also unexpectedly update the price.

    So it was decided - we will design and manufacture the device ourselves. Preliminary requests for the cost of the main components spoke of the ability to meet the initial 45rmb / pc. Also in the public domain a large number of open projects that are worth exploring in order to ensure a quick start to development.

    A quick search gave a publication about Chinese routers on Habré - "Explore Chinese routers on RT5350 . "

    Another small selection of Chinese modules presented at www.indiegogo.com is"3 projects of inexpensive mini-PCs with Indiegogo . "

    A short list of links, the study of which helped the author in further work:
    www.indiegogo.com/projects/asiarf-tiny-linux-computer -with-wifi-and-ethernet # home




    WiFIDuino, VoCore and AWM002 projects combine the use of a cheap Ralink RT5350 chip with a 360 MHz MIPS processor ( WIFIDuino uses a WIFI module with this chip), plus 8 MB of FLASH memory and 32 MB of RAM.

    We ask the prices of the processor and memory from suppliers, again using www.1688.com. Hereinafter, prices are given for the quantity required for the production of 500 devices or at the minimum packaging rate. A quick survey of several suppliers now gives the following prices for the main components - Ralink RT5350 - 10.5rmb / pc, SDRAM 32MB - 5.1rmb / pc, SPI FLASH 8MB - 6rmb / pc. Reasonable prices - taking into account the printed circuit board and installation, they must meet the planned 45rmb / pc.

    Of the above projects, a very good impression was made by VoCore, which was pretty well lit on the hub. Therefore, in further work we used it as an example.

    We draw a schematic diagram in the editor, put down all the values ​​of the components.

    The scheme is necessary to generate a list of elements and purchase components, as well as, of course, for the further design of the printed circuit board.

    Here it is worth recalling the requirements of the customer about the use of certain dimensions. Therefore, before completing the final trace, we perform an additional step in coordinating the position of the components on the printed circuit board. For this purpose, 3-dimensional components used in the circuit were drawn, and a 3-dimensional model of the device was created. Subsequent reconciliation revealed a couple of comments on the position of the components, which were immediately fixed. The LED did not fall into the hole of the planned housing and the dimensions of the board were slightly increased.

    After an intermediate check - proceed to the trace. The board will be 4-layer with impedance control of the 5th accuracy class. We perform PCB tracing taking into account the requirements of the technical specifications, as well as using the previously prepared circuit diagram and 3-dimensional components. According to estimates, the draft trace should not take more than one day, subsequent coordination and refinement of up to 5 days. As a result of hard work, the board acquired the following form.

    So, the board design is ready - it's time to order printed circuit boards. First of all, you need to prepare the files for production. We need gerber files, not just boards, but a multiplied blank. The panel (multiplied blank) contains several copies of the printed circuit board. It is used to optimize production - roughly speaking at all stages several boards are manufactured / assembled at a time. In addition, since we have a two-way SMT installation, to save time and money, we make a tricky panel symmetrical with respect to 180 degrees rotation.

    We place an order for prototypes of printed circuit boards and a week later - we become happy owners of nice boards.

    I must say that in parallel with the production of printed circuit boards, the purchase of components was successfully completed and the date of the start of installation at the SMT factory was agreed. We transfer the list to installation, wait 3 days and the devices are ready.

    Normative control of soldering using x-rays when using BGA-cases is required.

    The most important thing is ahead - we are starting to set up. Unfortunately, a few simple errors crept into the project, so I had to resort to a heat-resistant wire for modification. Also, some ratings of passive components have changed.

    The first functional test - we use the newly created "Chinese router" to organize a WiFi-Ethernet bridge for a laptop. For the first check, we try to download a couple of files. Successful - a stable download speed and a reliable WiFi signal level indicate the possibility of further testing and testing.

    In total, the first stage of the project has been completed: there are live prototypes suitable for functional testing together with the customer. Ahead is a series of checks on the basis of which a decision will be made either on completion or on the start of mass production.

    As already noted, the estimated cost of the device is 38rmb / pc for the production of a batch of 500 pieces. Production time 2 weeks. The amount of 38rmb, of course, is significantly less than 65rmb declared by the Chinese for custom routers and less than 60rmb for ready-made ones, which justifies the time and effort spent on the project.

    Development took 80 man-hours, although due to the desire to limit costs, it stretched for 2 months. Approximately up to 80 hours are required for testing and refinement.

    For this, I thank the readers for the time spent, the customer for patience, and the Chinese for hard work.

    PS At the time of publication, the exchange rate is USD / RMB = 6.2, RMB / RUB = 10.5. Please do not minus for the provision of figures in Chinese currency, but calculate it yourself in your mind, since exchange rates are constantly changing.

    PPS We do not plan to make iron an open project, so the circuit diagram is not laid out in very good quality. Believe me, the typical scheme.

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