VP Process Inc has just released a new 4 channel Analog Output 4-20mA Interface, the PI-SPI-DIN-4AO.
The 4AO is based on the Microchip MCP4728 12 bit DAC with I2C interfacing. The MCP4728 has up to 8 programmable I2C addresses, which means 8 of these modules can be daisy chained together for a total of 32 analog output 4-20mA signals. Combine this module with the other modules in this series, you now have some serious process control interfacing capability!
The I2C interface has a bidirectional buffer that isolates capacitance and allows for up to 1MHz speeds and up to 4000pF at lower speeds. The PI-SPI-DIN-RTC-RS485 has the same buffer to drive the longer cables associated with this series.
Each of the 4 channels of 4-20mA analog output has a signal strength LED, can drive up to 1000 Ohms when the main filed power is 24 VDC. The output circuit is the sme as the PI-SPI-2AO module.
Sample I2C code (written in C) can be found as a download on the product page.