CHIP i2c and GPIO in Gforth

C.H.I.P. i2c and GPIO low level and other code to access devices with Gforth

• CHIP_Gforth_i2c.fs

  • This file makes low level reading and writing to CHIP i2c work in gforth. At this writing I have confirmed on headless OS 4.4 that U14 pin25 and pin26 ( TWI2-SDA(i2c-2-SDA) & TWI2-SCK(i2c-2-SCL) ) work without a device overlay added to the OS. I talked to a BMP180 device at i2c address #77 with the below gforth software for this sensor. Use this as follows at the command line:

  sudo gforth CHIP_Gforth_i2c.fs

  • I added an ability to force an i2c connection to CHIPi2copen word. Realize this could damage devices and or confuse the kernel so use with caution! This means the sysfs stuff that is working with i2c devices will get confused when you start forcing i2c connections but on the other hand if you simply use this and not the sysfs stuff then it does not really matter right. After all i treat the chip as a powerfull microcontroller!

• BMP180-object.fs

  • This file is an object that can be used to talk to the BMP180 sensor provided it is connected to U14 pin25 and pin26 for i2c-2 connection. I have confirmed at this writing that this does work with the above CHIP_Gforth_i2c i2c low level words. Use this as follows at the command line:

  sudo gforth BMP180-object.fs

  Now once in gforth to read the sensor do the following:

  bmp180-i2c heap-new constant mybmp180
  mybmp180 display-tp
  mybmp180 read-temp-pressure throw cr ." pressure:" . cr ." temperature:" .
  

  This example shows two ways to read the data from the object called bmp180-i2c.

• CHIP_battery_lvl.fs

  • This file talks to the AXP209 device on the CHIP board to get the battery voltage if you have one connected. Use this example as guidance to talk to the AXP209 device for other information. I got the idea from the file at /usr/bin/battery.sh found on headless chip os 4.4. Note the AXP209 device seems to be on i2c bus address 0 and this bus is used by the kernel. So to get around this i added the ability to force an i2c connection when opening the handle with the CHIP_Gforth_i2c.fs code. This force a connection method could cause damage to i2c devices and or confuse the kernel so use this with care.

• clean-myGforth_i2c-libs

  • This file is a simple bash script to delete the shared library files that are created when you use CHIP_Gforth_i2c.fs the first time. Use this file to remove the shared library when an update happens on this git repository for the CHIP_Gforth_i2c.fs library.

• CHIP_GPIO_via_XIOpins.fs

  • The i2c device PCF8574A used on CHIP board is an gpio type expander. There are pins labeled XIO-P0 to XIO-P7 on u14 header that connect to this gpio expander. This code simply provides read and write type words to use those pins as GPIO.
    The method used to talk to the GPIO expander is a force type method... This means the sysfs stuff could get confused so if using this method then do not use the sysfs stuff!

• i2c-information.md

  • Information file about CHIP and i2c!