Turn: Talking about am335x hardware system design from Beaglebone

Link: http://blog.chinaunix.net/uid-730738-id-3266690.html chenzhufly

Discussion on am335x hardware system design from Beaglebone

Date: 2012-04-25 If it is not to try Beaglebone, will not spend a lot of time to study the am335x hardware system design, these days through TI a lot of documents, some small experience, and everyone share, all as a record, a long time can come back to turn over. About am335x Hardware system introduction can refer to this link: http://processors.wiki.ti.com/index.php/AM335x_Hardware_Design_Guide

= = Hardware Design timeline→==

constructing the Block Diagram

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selecting the Boot Mode

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confirming Pin multiplexing compatibility

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confirming Electrical and Timing compatibility

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designing the Power Subsystem

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designing The Clocking Subsystem

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floorplanning the PCB

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creating the Schematics

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laying out the PCB

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testing/debugging

I mainly in the following order, talk about my recent gains, for your reference only.  Beaglebone's Reference manual:"Beaglebone Rev A3 System Reference Manual" 1) About powerTI is always propaganda am335x as long as 5 dollars, you are looking at it supporting the use of power chips, the price is not cheap ah, are around 4 dollars, really fucking pit Dad!      and the choice of power chip room is not big, this is a good thing for the system design, do not have too much tangle, the use of mature programs on the line. Common collocation: can refer to "am335x Power Options" Also on these several materials, AM335X_EVM use is TPS65910, in Beaglebone use is TPS65217 have the following several documents can refer to: TPS65217 User's Guide for am335x processors (SLVU551) "tps65910a user ' s guidelines for am335x processors (SWCU093)" Powering the am335x With the TPS650250 (SLVA487) "

"Power Management Units for Embedded processors"

This link is written in more detail: http://processors.wiki.ti.com/index.php/Device:AM335x:Device_Evaluation Beaglebone on the use of TPS65217 is also very interesting , see, there are three kinds of a,b,c, what is the difference?  Look at the chart below and it might be instructive. It's obvious that we're using tps65217b, why? AM3359 only Zcz package, onboard memory is DDR2. So how many kinds of power do AM3359 have? "In am335x Arm®cortex™-a8 microprocessors (MPUs)" On the 77th page has a detailed introduction, mainly 1.1v,1.8v,3.3v in different modes, the system's frequency is not the same, the Vdd_mpu,vdd_  The core voltage requirements are also different. Why a special power supply chip is required, it is estimated that it is related to the power-up sequence of each source. Ordinary power chip can not meet the requirements of the system design, at present do not see the mature program, who do not want to be a small white mouse, or the flow of the good. Am335x the power-up sequence for each voltage is as follows: because the trial board was A3 version, and the chip model is also XAM3359, belongs to the experimental sample, not marked the rate of the chip, and do not know how fast to run. However, from the Linux system printing, it should be in 500MHz or 600MHz  IO voltage also has two, 1.8V or 3.3V from the above figure can see this,supply voltage range for Dual-voltage IO domainBeaglebone is directly connected to the 3.3V on the schematic diagram of the Beaglebone Rev3 can be obtained from this address: https://github.com/CircuitCo/BeagleBone-RevA3 Evaluation of power dissipation at this address can be seen: http://processors.wiki.ti.com/index.php/AM335x_Power_Consumption_Summary, or very detailed 2) About clocks  Detailed details refer to datasheet bar, the main two sentences:

• The device operation requires a 32k optional crystal and HF crystal with either 19.2,24,25,26 MHz reference clock for Oper ation.
• A 32.768-khz Clock Input is an optional for the RTC.

The Beaglebone uses a 24MHz external clock, the schematic is as follows: As for the internal main clock and external input clock is what relationship, this also needs further research, but not much of the hardware design itself. 3) About startup modeThe following boot modes is supported:

• NOR Flash Boot
• NAND Flash Boot
• SPI Boot
• SD/MMC Boot
• EMAC Boot
• UART Boot
• USB boot (like a Ethernet card, not as mass storage)

 The first 4 should be the most popular starting mode, Norflash now with the file system and applications continue to expand, has gradually declined. Now the more flourishing should be from the Nandflash start beaglebone at present is just from the SD card boot, this in the debugging phase is very convenient, do the production of the words are some far-fetched, at least I was not recommended to usehere has to mention the beauty of a memory chip, model: Mt29cxgxxmaxxxjaWhat's Special: 137-ball NAND Flash with Lp-dram MCP, which is a memory with both NAND and Lp-dramjust this am335x all support, such a memory I like. The system can be designed more compact, and no SD card boot, suitable for product development. at the same time I have seen the success of the case, DM3730 + this material
About the system start-up process is not discussed in this, there is time to speak alone   4) about the network port  No, not all advertised have gigabit network mouth, I go through all the and am335x related to the demo board, are hundred trillion network mouth, this is why?? Why is this??? Seemingly beaglebone interface is the Mii interface, only and the manual Rgmii interface similar, but the clock is 25MHz, the rate only to 100M Ah, is not replaced by 125M can be 1000M? But LAN8710 also do not support gigabit network, haha. Oh, that's weird. Popular Science: RGMII (reduced Gigabit media independent Interface) is a reduced GMII (Gigabit Media Standalone interface). The Gmii and Rgmii are 8-bit data interfaces with a working clock of 125MHz, so the transfer rate can be up to 1000Mbps. At the same time, compatible with the MII 10/100 Mbps operating mode, support transmission rate: 10M/100M/1000MB/S, the corresponding CLK signal is: 2.5mhz/25mhz/125mhz. The RGMII data structure conforms to the IEEE Ethernet standard and the interface definition is shown in IEEE 802.3-2000.

Turn: Talking about am335x hardware system design from Beaglebone