Gravimetric

A controller board with ATmega324pb set up for measuring event times using ICP1, ICP3, and ICP4 with RJ45 for multi-drop serial. Two UART or digital IO (RX1, TX1, RX2, TX2) have level shift. Four analog channels (0..3) also work as digital IO. Seven 22mA current source for use with loop sensors, SSR, LED, and other. Three 17mA current source for flow sensor (ICP1) and start/stop switches (ICP3, and ICP4). Input capture occurs when when enough current (>7mA) arrives at the 100 Ohm loop sensor. Alternate power input may be enabled (ALT_EN), and power to SBC may be disabled (PIPWR_EN). SPI pins are connected to the SBC. Bus manager (ATmega328pb) is a slave I2C (TWI0) connected to ATmega324pb master (TWI0) and a slave SMbus (TWI1) connected to SBC. Power with 7 thru 36V DC.

GitHub

Use a Raspberry Pi Zero as a host to do In-Circuit Serial Programming of AVR’s. IOFF buffers are used to level convert to the targets voltage. It also allows the serial port to be used for serial bootload and has some switches to control looping of the upload.

ICSP

ICSP

Use a Raspberry Pi Zero as a host to do In-Circuit Serial Programming of AVR’s. IOFF buffers are used to level convert to the targets voltage. It also allows the serial port to be used for serial bootload and has some switches to control looping of the upload.

ICSP

RPUpi

This shield or mezzanine is how I place a tool-chain at the network edge. It has full duplex communications and management done with RS485 transceivers over CAT5. The SBC computer I use is a Raspberry Pi Zero (I suspect others may work). The serial is multidrop so the computer can communicate with several targets (e.g. RPUno, RPUlux, Irrigate7…). Management allows selecting a target for bootload with the tool-chain uploader. I have been using the AVR toolchain with this, but the plan is to try SAM-BA and BOSSA. I use SSH connections to compile the bare metal programs and then the uploader without involving any networking (note using the serial requires that the user be in the dialout group). The bare metal has no exposed network surface.

RPUpi Forum HackADay

USBuart

FT231X and a 74LVC07A buffer allow connecting serial devices (e.g. RPUadpt) that have there own power in the 1.8V to 5V range. When the serial port nRTS is pulled active a 17mA current source will try to power the buffer (for RPUadpt), but it will not be enough to power most serial hardware so they will need there own power. When the buffer is not powered it is in an IOFF condition.

GitHub