rnd:projects:aft

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rnd:projects:aft [2022-12-22 04:21] – asdfrnd:projects:aft [2023-05-07 02:54] (current) – asdf
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 ==== SFP modules ==== ==== SFP modules ====
-SFPs (small form-factor pluggable) are compact IR transceivers designed for fiber optic networking. There are two major advantages to using an SFP in this device. First, it puts the tester on equal footing with the devices in the live environment. We don't have to worry about propagation distances; if the tester can't transmit over the entire fiber run, then neither will a switch be able to. Second, it allows the tester to check the SFP itself using DDM/DOM [(ddm_dom)] or I2C [(sfp_i2c)]. In the future, we may also be able to program the tester to talk to live network devices to help determine where the other end of the cable goes((It seems likely that an Arduino Uno is not fast enough to process Ethernet frames. One of the beefier boards may, but this feature is not essential for the tester as described.)).+SFPs (small form-factor pluggable) are compact IR transceivers designed for fiber optic networking. There are two major advantages to using an SFP in this device. First, it puts the tester on equal footing with the devices in the live environment. We don't have to worry about propagation distances; if the SFP-equipped tester can't transmit over the entire fiber run, then neither will a switch be able to. Second, it allows the tester to check the SFP itself using DDM/DOM [(ddm_dom)] or I2C [(sfp_i2c)]. In the future, we may also be able to program the tester to talk to live network devices to help determine where the other end of the cable goes((It seems likely that an Arduino Uno is not fast enough to process Ethernet frames. One of the beefier boards may, but this feature is not essential for the tester as described.)).
  
 The electrical pinout is shown in {{ref>tab_sfp_pinout}}. The electrical pinout is shown in {{ref>tab_sfp_pinout}}.
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 | 20 | VeeT | Transmitter ground | | 20 | VeeT | Transmitter ground |
 </table> </table>
 +
 +<WRAP center round tip 60%>
 +The ''Tx_disable'' pin is connected to an internal pull-up resistor inside the module. This pin must be pulled low to enable the transmit laser.
 +</WRAP>
  
 ==== Osmocom SPF experimenter ==== ==== Osmocom SPF experimenter ====
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 SFP modules expose a great deal of data detailing their internal status, all accessible through I2C at one of two addresses (''0xA0'', ''0xA2''). Before data can be read, the EEPROM address must be loaded in by performing a dummy write containing the 8-bit EEPROM address to retrieve. For example, the device vendor name is stored in 16 bytes at I2C address ''0xA0'', EEPROM address 20. The following snippet demonstrates this procedure. SFP modules expose a great deal of data detailing their internal status, all accessible through I2C at one of two addresses (''0xA0'', ''0xA2''). Before data can be read, the EEPROM address must be loaded in by performing a dummy write containing the 8-bit EEPROM address to retrieve. For example, the device vendor name is stored in 16 bytes at I2C address ''0xA0'', EEPROM address 20. The following snippet demonstrates this procedure.
  
-<code c>+<code cpp>
 // load in the EEPROM address // load in the EEPROM address
 Wire.beginTransmission(0x50); Wire.beginTransmission(0x50);
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 After each read, the internal address register is incremented so it points to the next byte. Given the way we're most likely to access this table, this fact is of relatively little use to us. After each read, the internal address register is incremented so it points to the next byte. Given the way we're most likely to access this table, this fact is of relatively little use to us.
  
 +<table |tab_sfpreg_50>
 +<caption>Registers of interest at I2C address 0x50</caption>
 +
 +<datatables paging="false">
 +^ Value ^ Address (dec) ^ Data length ^
 +| Manufacturer name (ASCII) | 20 | 16 |
 +| Compliance code | 3 | 8 |
 +| Nominal signalling rate (100s Mbd) | 12 | 1 |
 +| Supported optional DDM features | 93 | 1 |
 +</datatables>
 +</table>
 +
 +<table |tab_sfpreg_51>
 +<caption>Registers of interest at I2C address 0x51</caption>
 +
 +<datatables paging="false">
 +^ Value ^ Address (dec) ^ Data length ^
 +
 +</datatables>
 +</table>
 ==== Serial data transmission ==== ==== Serial data transmission ====
  
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 </table> </table>
  
 +==== Communication ====
 +UART transmission is not looking terribly promising at this time. 
 +
 +Different SFP models appear to produce different signals when the output is open. The SMF unit (unknown vendor) outputs nothing, while the Veloso units send (noisy) pulse trains (see {{ref>fig_idle}}). They also respond differently to inputs, with the former producing an inverted replica of the input and the latter outputting what might be PWM ({{ref>fig_k}}).
 +
 +<figure center|fig_idle>
 + <subfigure |fig_smf_idle>
 + {{ :rnd:projects:smf-idle.png?400 |}}
 +<caption>SMF</caption>
 + </subfigure>
 + <subfigure |fig_veloso_idle>
 + {{ :rnd:projects:veloso-idle.png?400 |}}
 +<caption>Veloso</caption>
 + </subfigure>
 +<caption>Idle responses from signal loopback</caption>
 +</figure>
 +
 +<figure center|fig_k>
 + <subfigure |fig_smf_k>
 + {{ :rnd:projects:smf-k.png?400 |}}
 +<caption>SMF</caption>
 + </subfigure>
 + <subfigure |fig_veloso_k>
 + {{ :rnd:projects:veloso-k.png?400 |}}
 +<caption>Veloso</caption>
 + </subfigure>
 +<caption>Responses to UART ''k'' at 115200 baud, 8N1</caption>
 +</figure>
 ==== Power considerations ==== ==== Power considerations ====
 Portable operation is a must for this tester. Portable operation is a must for this tester.
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   * [[https://github.com/Stutchbury/EncoderButton]]   * [[https://github.com/Stutchbury/EncoderButton]]
   * [[https://www.instructables.com/Manchester-Code-Library-for-Arduino/]], [[https://github.com/mdeudon/Manchester]], [[wp>manchester code]]   * [[https://www.instructables.com/Manchester-Code-Library-for-Arduino/]], [[https://github.com/mdeudon/Manchester]], [[wp>manchester code]]
 +  * https://www.ti.com/lit/ug/tidu366/tidu366.pdf
 +  * https://cdn.hackaday.io/files/21599924091616/AN_2030_DDMI_for_SFP_Rev_E2.pdf
 +  * https://gitea.osmocom.org/electronics/osmo-small-hardware/raw/branch/master/sfp-breakout/sfp-experimenter.pdf
 +  * https://www.ti.com/lit/ds/symlink/sn65lvds1.pdf?ts=1672100269172&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FSN65LVDS1%252Fpart-details%252FSN65LVDS1D%253Futm_source%253Dgoogle%2526utm_medium%253Dcpc%2526utm_campaign%253Docb-tistore-promo-asc_opn_en-cpc-storeic-google-wwe%2526utm_content%253DDevice%2526ds_k%253DSN65LVDS1D%2526DCM%253Dyes%2526%2526utm_source%253Dgoogle%2526utm_medium%253Dcpc%2526utm_campaign%253D%2526utm_content%253D%2526ds_k%253Dsn65lvds1d%2526DCM%253Dyes%2526gclid%253DCjwKCAiAqaWdBhAvEiwAGAQltruYrSedpQ0uALxXlAq5xiuhmzbVhkdHlCKyi0L3cz9s1VCdN4uf8xoCVpwQAvD_BwE%2526gclsrc%253Daw.ds
 +  * https://hackaday.com/2020/05/11/new-teensy-4-1-arrives-with-100-mbps-ethernet-high-speed-usb-8-mb-flash/
 +  * https://twitter.com/PA4DAN/status/1108517564005695491/photo/1
 +  * https://www.fluxlight.com/content/Tech-Docs/AdTran%2012004800%20Datasheet.pdf
 +  * https://hackaday.com/2021/02/13/experiment-with-sfp-modules-with-this-handy-breakout/
    
 ===== References ===== ===== References =====
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 [(sparkfun_serialcomm>https://learn.sparkfun.com/tutorials/serial-communication)] [(sparkfun_serialcomm>https://learn.sparkfun.com/tutorials/serial-communication)]
 [(twi_protocol>https://ww1.microchip.com/downloads/en/devicedoc/doc0180.pdf)] [(twi_protocol>https://ww1.microchip.com/downloads/en/devicedoc/doc0180.pdf)]
 +
 +{{tag>electronics}}
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