TMC2225 DATASHEET (Rev. 1.15 / 2023-FEB-16)
18
4.4 Addressing Multiple Nodes
WRITE ONLY ACCESS
If read access is not used, and all nodes are to be programmed with the same initialization values, no
addressing is required. All nodes can be programmed in parallel like a single device (Figure 4.1.).
ADDRESSING MULTIPLE NODES
As the TMC2225 uses a fixed UART address, in principle only one IC can be accessed per UART
interface channel. Adding analog switches allows separated access to individual ICs. This scheme is
similar to an SPI bus with individual node select lines (Figure 4.2).
TMC22xx
#1
TMC22xx
#2
TMC22xx
#3
+VIO
+VIO
+VIO
Master CPU
(µC with UART)
Port pin
Port pin
Port pin
Port pin
TXD
1k
22k
Select#1
74HC1G125
¼ 74HC4066
RXD
Optional buffer for
transmission over long
lines or many slaves.
22k
Select#2
¼ 74HC4066
22k
Select#3
¼ 74HC4066
Figure 4.2 Addressing multiple TMC2225 via single wire interface using analog switches
PROCEED AS FOLLOWS TO CONTROL MULTIPLE NODES:
- Set the UART to 8 bits, no parity. Select a baud rate safely within the valid range. At
250kBaud, a write access transmission requires 320µs (=8 Bytes * (8+2) bits * 4µs).
- Before starting an access, activate the select pin going to the analog switch by setting it high.
All other nodes select lines shall be off unless a broadcast is desired.
- When using the optional buffer, set TMC2225 transmission send delay to an appropriate value
allowing the µC to switch off the buffer before receiving reply data.
- To start a transmission, activate the TXD line buffer by setting the control pin low.
- When sending a read access request, switch off the buffer after transmission of the last stop
bit is finished.
- Take into account, that all transmitted data also is received by the RXD input.
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