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diff --git a/posts/2013-12-09-wavedrum-connectors.skr b/posts/2013-12-09-wavedrum-connectors.skr new file mode 100644 index 0000000..a6382ed --- /dev/null +++ b/posts/2013-12-09-wavedrum-connectors.skr @@ -0,0 +1,149 @@ +(define meta + `((title . "Connectors on the Wavedrum’s circuit board") + (date . ,(string->date* "2013-12-09 00:00")) + (tags "DIY" "electronics" "music" "hacking" "wavedrum"))) + +(list + + (p [On the circuit board of the Wavedrum there are solder holes to + accomodate three large connectors. Since they are so easily + accessible and thus very inviting to anyone interested in + modifying the instrument, I decided to trace each of the pins to + its destination.]) + + (p [The three connectors are named CN10, CN11, and CN12, + respectively. CN10 is found on the bottom right, CN11 on the + bottom left, and CN12 close to the left edge below the micro SD + card reader.]) + + (wide-img "2013/wavedrum-connectors.jpg" + "connectors on the mainboard") + + (h2 [CN10: digital audio interface]) + + (p [Most of the ten pins of CN10 are outputs. The first three pins + carry clock signals used by the analogue to digital and digital + to analogue converters on the top-side of the board. Pin four + gives access to the PDN (power down) signal which is used to + disable the converters. The next three pins are connected over + the resistors R85, R84, and R83 to the DSP's pins 145, 144, and + 143 (respectively); according to the ,(ref + "http://www.analog.com/static/imported-files/data_sheets/ADSP-21371_21375.pdf" + "DSP's datasheet") these pins are ,(code [DAI_P8]) (,(code [SFSI])), ,(code [DAI_P10]) + (,(code [SD2B])), and ,(code [DAI_P11]) (,(code [SD3A])), and are thus part of the + Digital Audio Interface (DAI). The remaining three pins on CN10 + expose the supply voltage, ground, and an alternative positive + voltage (the same as on the plus pole of the silver capacitors + near the right edge of the board). These are the signals left to + right:]) + + (table :align '("right") + :headers '("" "direction" "description") + :rows + '(("1" "output" "Master clock") + ("2" "output" "Audio serial clock") + ("3" "output" "Left/right clock") + ("4" "output" ((code "PDN") " (power down)")) + ("5" "input?" ((code "DAI_P8") " / " (code "SFSI"))) + ("6" "input?" ((code "DAI_P10") " / " (code "SD2B"))) + ("7" "input?" ((code "DAI_P11") " / " (code "SD3A"))) + ("8" "output" ((code "V_A") ", or " (code "V_DD"))) + ("9" "output" "GND") + ("10" "output" "alternative positive voltage"))) + + (p [What is this all good for? Well, since all these clocks and + voltages are exported it becomes relatively easy to connect an + external digital to analogue converter (when ,(code [DAI_P8]), + ,(code [DAI_P10]), and ,(code [DAI_P11]) are used as outputs), or + an external analogue to digital converter (if the DSP pins are + used as inputs instead). nAs there are protective resistors + between the DSP pins and the connector pins 5–7 I assume that + they are supposed to be used as inputs.]) + + + (h2 [CN11: JTAG interface]) + + (p [Moving on to the left bottom edge of the board we see a 14-pin + connector with the name CN11. This connector gives access to the + JTAG interface on the DSP, which allows system debugging. + Unfortunately, I don't own a JTAG dongle and the free JTAG + debugger ,(ref "http://openocd.sourceforge.net" "OpenOCD") does + not support the SHARC core, so I haven't been able to experiment + with the debugging interface. I'm not sure whether it is + possible to use debugging feature without hardware/software + provided by Analog Devices. Using JTAG it should be possible to + overwrite the flash memory and replace the firmware. This is the + most promising method to upgrade (or downgrade) a Wavedrum.]) + + (p [The pins on the bottom row are all connected to ground, so the + following table only lists the signal names of the upper row of + the connector in order from left to right:]) + + (table :align '("right") + :headers '("" "Signal" "Full name") + :rows + '(("1" (code [~EMU]) "Emulation status") + ("2" (code [GND]) "Ground") + ("3" (code [TMS]) "Test mode select") + ("4" (code [TCK]) "Test clock") + ("5" (code [~TRST]) "Test reset") + ("6" (code [TDI]) "Test data input") + ("7" (code [TDO]) "Test data output"))) + + (h2 [CN12: two-wire serial interface]) + + (p [CN12 exposes the DSP's two-wire interface, a serial interface + compatible with the proprietary I^2C interface. This allows us + to connect a number of external serial devices to the serial bus. + As firmware support is required to communicate with the devices + on the serial bus I don't see how this could be used without a + custom firmware.]) + + (p [The following table lists the signals from top to bottom:]) + + (table :align '("right") + :headers '("" "Signal" "Full name") + :rows + '(("1" (code [V_D]) "Positive voltage") + ("2" (code [TWI_DATA]) "Two-wire interface data") + ("3" (code [TWI_CLK]) "Two-wire interface clock") + ("4" (code [GND]) "Ground"))) + + + (h2 [Bonus: boot mode]) + + (p [What led me to tracing the routes of the connectors was my + curiosity about the boot mode. According to the DSP's datasheet, + there are four possible boot modes to select from by playing with + the states of the pins ,(code [BOOT_CFG1-0]) (one of these boot + modes is “no boot”). Tracing these two pins from the DSP it + becomes clear that the third boot mode “EPROM/FLASH boot” is + hardwired (,(code [BOOT_CFG1-0 = 10])). The other two usable + boot modes are SPI master and slave boots.]) + + (table :align '("right") + :headers '("BOOT_CFG1-0" "Booting mode") + :rows + '(("00" "SPI Slave Boot") + ("01" "SPI Master Boot") + ("10" "EPROM/Flash Boot") + ("11" "No boot"))) + + (wide-img "2013/wavedrum-bootcfg.jpg" + "boot configuration traces") + + (p [As can be seen on the photo, the Wavedrum engineers were kind + enough to leave solder pads connected to boot configuration pins + on the board, allowing us to rewire them as we see fit. To set + ,(code [BOOT_CFG0]) the pads for ,(code [R72]) have to be + bridged; likewise, to clear ,(code [BOOT_CFG1]) only the two pads + of ,(code [R59]) have to be bridged.]) + + + (h2 [References]) + + (ul + (li [,(ref "http://www.analog.com/static/imported-files/data_sheets/ADSP-21371_21375.pdf" + "ADSP-21371/ADSP-21375 datasheet")]) + (li [,(ref "http://www.analog.com/static/imported-files/processor_manuals/ADSP-21367_hwr_rev2-1.pdf" + "ADSP hardware reference")]))) |