do not set SPI_NO_CS bit when chip is AM3358 #104

Avoid trying to set SPI_NO_CS mode bit when the chip is AM3358 as this
will always fail as Linux kernel driver omap2_mcspi does not support it.

This applies to the BeagleBone Black and PocketBeagle.

For testing, BME280 was wired to SPI0 peripheral on BeagleBone Black.

Run these commands to make sure the pins are in the correct mode:

config-pin p9.13 gpio     # GPIO used for CS
config-pin p9.18 spi      # SPI0_D1 (MOSI)
config-pin p9.21 spi      # SPI0_D0 (MISO)
config-pin p9.22 spi_sclk # SPI0_SCLK

SPI0 was accessed via /dev/spidev0.0

diff --git a/src/adafruit_blinka/microcontroller/generic_linux/spi.py b/src/adafruit_blinka/microcontroller/generic_linux/spi.py
index a8141b96a0e84a0c90c1f5eab05502f8fede8754..cc19cd89312679e6a09450980f5ab9ffa76c3901 100755 (executable)
--- a/src/adafruit_blinka/microcontroller/generic_linux/spi.py
+++ b/src/adafruit_blinka/microcontroller/generic_linux/spi.py
@@ -1,5 +1,6 @@
 import spidev
 import time
+from adafruit_blinka.agnostic import detector
 
 class SPI:
     MSB = 0
@@ -29,6 +30,19 @@ class SPI:
         self.baudrate = baudrate
         self.mode = mode
         self.bits = bits
+        self.chip = detector.chip
+
+    def set_no_cs(self):
+        # Linux SPI driver for AM33XX chip in BeagleBone and PocketBeagle
+        # does not support setting SPI_NO_CS mode bit (issue #104)
+        if not self.chip.AM33XX:
+            try:
+                self._spi.no_cs = True  # this doesn't work but try anyways
+            except AttributeError:
+                pass
+        else:
+            # TODO: remove this debug output
+            print("Adafruit_Blinka: generic_linux/spi.py: set_no_cs(): detected AM33XX, SKIP setting no_cs")
 
     def write(self, buf, start=0, end=None):
         if not buf:
@@ -37,10 +51,7 @@ class SPI:
             end = len(buf)
         try:
             self._spi.open(self._port, 0)
-            try:
-              self._spi.no_cs = True  # this doesn't work but try anyways
-            except AttributeError:
-              pass
+            self.set_no_cs()
             self._spi.max_speed_hz = self.baudrate
             self._spi.mode = self.mode
             self._spi.bits_per_word = self.bits
@@ -57,10 +68,7 @@ class SPI:
             end = len(buf)
         try:
             self._spi.open(self._port, 0)
-            try:
-              self._spi.no_cs = True  # this doesn't work but try anyways
-            except AttributeError:
-              pass
+            self.set_no_cs()
             self._spi.max_speed_hz = self.baudrate
             self._spi.mode = self.mode
             self._spi.bits_per_word = self.bits
@@ -84,10 +92,7 @@ class SPI:
             raise RuntimeError('Buffer slices must be of equal length.')
         try:
             self._spi.open(self._port, 0)
-            try:
-                self._spi.no_cs = True  # this doesn't work but try anyways
-            except AttributeError:
-                pass
+            self.set_no_cs()
             self._spi.max_speed_hz = self.baudrate
             self._spi.mode = self.mode
             self._spi.bits_per_word = self.bits