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Diffstat (limited to 'Documentation/spi/spi-lm70llp')
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diff --git a/Documentation/spi/spi-lm70llp b/Documentation/spi/spi-lm70llp deleted file mode 100644 index 463f6d01fa15..000000000000 --- a/Documentation/spi/spi-lm70llp +++ /dev/null @@ -1,79 +0,0 @@ -spi_lm70llp : LM70-LLP parport-to-SPI adapter -============================================== - -Supported board/chip: - * National Semiconductor LM70 LLP evaluation board - Datasheet: http://www.national.com/pf/LM/LM70.html - -Author: - Kaiwan N Billimoria <kaiwan@designergraphix.com> - -Description ------------ -This driver provides glue code connecting a National Semiconductor LM70 LLP -temperature sensor evaluation board to the kernel's SPI core subsystem. - -This is a SPI master controller driver. It can be used in conjunction with -(layered under) the LM70 logical driver (a "SPI protocol driver"). -In effect, this driver turns the parallel port interface on the eval board -into a SPI bus with a single device, which will be driven by the generic -LM70 driver (drivers/hwmon/lm70.c). - - -Hardware Interfacing --------------------- -The schematic for this particular board (the LM70EVAL-LLP) is -available (on page 4) here: - - http://www.national.com/appinfo/tempsensors/files/LM70LLPEVALmanual.pdf - -The hardware interfacing on the LM70 LLP eval board is as follows: - - Parallel LM70 LLP - Port Direction JP2 Header - ----------- --------- ---------------- - D0 2 - - - D1 3 --> V+ 5 - D2 4 --> V+ 5 - D3 5 --> V+ 5 - D4 6 --> V+ 5 - D5 7 --> nCS 8 - D6 8 --> SCLK 3 - D7 9 --> SI/O 5 - GND 25 - GND 7 - Select 13 <-- SI/O 1 - ----------- --------- ---------------- - -Note that since the LM70 uses a "3-wire" variant of SPI, the SI/SO pin -is connected to both pin D7 (as Master Out) and Select (as Master In) -using an arrangement that lets either the parport or the LM70 pull the -pin low. This can't be shared with true SPI devices, but other 3-wire -devices might share the same SI/SO pin. - -The bitbanger routine in this driver (lm70_txrx) is called back from -the bound "hwmon/lm70" protocol driver through its sysfs hook, using a -spi_write_then_read() call. It performs Mode 0 (SPI/Microwire) bitbanging. -The lm70 driver then inteprets the resulting digital temperature value -and exports it through sysfs. - -A "gotcha": National Semiconductor's LM70 LLP eval board circuit schematic -shows that the SI/O line from the LM70 chip is connected to the base of a -transistor Q1 (and also a pullup, and a zener diode to D7); while the -collector is tied to VCC. - -Interpreting this circuit, when the LM70 SI/O line is High (or tristate -and not grounded by the host via D7), the transistor conducts and switches -the collector to zero, which is reflected on pin 13 of the DB25 parport -connector. When SI/O is Low (driven by the LM70 or the host) on the other -hand, the transistor is cut off and the voltage tied to it's collector is -reflected on pin 13 as a High level. - -So: the getmiso inline routine in this driver takes this fact into account, -inverting the value read at pin 13. - - -Thanks to ---------- -o David Brownell for mentoring the SPI-side driver development. -o Dr.Craig Hollabaugh for the (early) "manual" bitbanging driver version. -o Nadir Billimoria for help interpreting the circuit schematic. |