Rehan
SPI not working on beaglebone
Hi all,
I’m running Nerves on a BeagleBone Black and trying to use SPI from Circuits.SPI.
I can see the devices in /dev:
/dev/spidev0.0
/dev/spidev0.1
/dev/spidev1.0
/dev/spidev1.1
But I’m having trouble confirming which header pins (P9/P8) are actually mapped to these devices under Nerves.
Questions:
- What is the correct mapping between
/dev/spidev0.0and BeagleBone header pins when using Nerves? - How can I verify from the Nerves IEx console (using only
File.read!,/proc/device-tree, or/sys/devices) that a given pin is really configured for SPI mode? - Is there a recommended way to enable or switch pinmux for SPI pins under Nerves since
config-pinis not available?
So far, I’ve opened SPI in IEx like this:
iex(1)> {:ok, ref}=Circuits.SPI.open("spidev0.0", speed_hz: 1_000_000, mode: 3)
{:ok, #Reference<0.2697461337.148504581.45500>}
iex(2)> Circuits.SPI.transfer(ref, <<0x80, 0x00>>)
{:ok, <<0, 0>>}
I’m not getting any response from the SPI slave. I’m using ADXL345 sensor expecting 0xE5 for above read operation
Example wiring to ADXL345 (3.3V SPI sensor)
- P9_17 (CS0)** → **ADXL345 CS
- P9_22 (SCLK)** → **ADXL345 SCL
- P9_18 (MOSI)** → **ADXL345 SDA (data in)
- P9_21 (MISO)** → **ADXL345 SDO (data out)
Am I Connecting to correct pins? Or pin mapping is different for spidev0.0
Thanks in advance.
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